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adding in privoxy directly to Orbot repo
2012-05-03 18:32:18 +00:00
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN""http://www.w3.org/TR/html4/loose.dtd">
<HTML
><HEAD
><TITLE
>Appendix</TITLE
><META
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CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK
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TITLE="Privoxy 3.0.12 User Manual"
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><BODY
CLASS="SECT1"
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><TR
><TH
COLSPAN="3"
ALIGN="center"
>Privoxy 3.0.12 User Manual</TH
></TR
><TR
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="bottom"
><A
HREF="seealso.html"
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ALIGN="right"
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>&nbsp;</TD
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></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="APPENDIX"
>14. Appendix</A
></H1
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="REGEX"
>14.1. Regular Expressions</A
></H2
><P
> <SPAN
CLASS="APPLICATION"
>Privoxy</SPAN
> uses Perl-style <SPAN
CLASS="QUOTE"
>"regular
expressions"</SPAN
> in its <A
HREF="actions-file.html"
>actions
files</A
> and <A
HREF="filter-file.html"
>filter file</A
>,
through the <A
HREF="http://www.pcre.org/"
TARGET="_top"
>PCRE</A
> and
<SPAN
CLASS="APPLICATION"
>PCRS</SPAN
> libraries.</P
><P
> If you are reading this, you probably don't understand what <SPAN
CLASS="QUOTE"
>"regular
expressions"</SPAN
> are, or what they can do. So this will be a very brief
introduction only. A full explanation would require a <A
HREF="http://www.oreilly.com/catalog/regex/"
TARGET="_top"
>book</A
> ;-)</P
><P
> Regular expressions provide a language to describe patterns that can be
run against strings of characters (letter, numbers, etc), to see if they
match the string or not. The patterns are themselves (sometimes complex)
strings of literal characters, combined with wild-cards, and other special
characters, called meta-characters. The <SPAN
CLASS="QUOTE"
>"meta-characters"</SPAN
> have
special meanings and are used to build complex patterns to be matched against.
Perl Compatible Regular Expressions are an especially convenient
<SPAN
CLASS="QUOTE"
>"dialect"</SPAN
> of the regular expression language.</P
><P
> To make a simple analogy, we do something similar when we use wild-card
characters when listing files with the <B
CLASS="COMMAND"
>dir</B
> command in DOS.
<TT
CLASS="LITERAL"
>*.*</TT
> matches all filenames. The <SPAN
CLASS="QUOTE"
>"special"</SPAN
>
character here is the asterisk which matches any and all characters. We can be
more specific and use <TT
CLASS="LITERAL"
>?</TT
> to match just individual
characters. So <SPAN
CLASS="QUOTE"
>"dir file?.text"</SPAN
> would match
<SPAN
CLASS="QUOTE"
>"file1.txt"</SPAN
>, <SPAN
CLASS="QUOTE"
>"file2.txt"</SPAN
>, etc. We are pattern
matching, using a similar technique to <SPAN
CLASS="QUOTE"
>"regular expressions"</SPAN
>!</P
><P
> Regular expressions do essentially the same thing, but are much, much more
powerful. There are many more <SPAN
CLASS="QUOTE"
>"special characters"</SPAN
> and ways of
building complex patterns however. Let's look at a few of the common ones,
and then some examples:</P
><P
><P
></P
><TABLE
BORDER="0"
><TBODY
><TR
><TD
> <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>.</I
></SPAN
> - Matches any single character, e.g. <SPAN
CLASS="QUOTE"
>"a"</SPAN
>,
<SPAN
CLASS="QUOTE"
>"A"</SPAN
>, <SPAN
CLASS="QUOTE"
>"4"</SPAN
>, <SPAN
CLASS="QUOTE"
>":"</SPAN
>, or <SPAN
CLASS="QUOTE"
>"@"</SPAN
>.
</TD
></TR
></TBODY
></TABLE
><P
></P
></P
><P
><P
></P
><TABLE
BORDER="0"
><TBODY
><TR
><TD
> <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>?</I
></SPAN
> - The preceding character or expression is matched ZERO or ONE
times. Either/or.
</TD
></TR
></TBODY
></TABLE
><P
></P
></P
><P
><P
></P
><TABLE
BORDER="0"
><TBODY
><TR
><TD
> <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>+</I
></SPAN
> - The preceding character or expression is matched ONE or MORE
times.
</TD
></TR
></TBODY
></TABLE
><P
></P
></P
><P
><P
></P
><TABLE
BORDER="0"
><TBODY
><TR
><TD
> <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>*</I
></SPAN
> - The preceding character or expression is matched ZERO or MORE
times.
</TD
></TR
></TBODY
></TABLE
><P
></P
></P
><P
><P
></P
><TABLE
BORDER="0"
><TBODY
><TR
><TD
> <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>\</I
></SPAN
> - The <SPAN
CLASS="QUOTE"
>"escape"</SPAN
> character denotes that
the following character should be taken literally. This is used where one of the
special characters (e.g. <SPAN
CLASS="QUOTE"
>"."</SPAN
>) needs to be taken literally and
not as a special meta-character. Example: <SPAN
CLASS="QUOTE"
>"example\.com"</SPAN
>, makes
sure the period is recognized only as a period (and not expanded to its
meta-character meaning of any single character).
</TD
></TR
></TBODY
></TABLE
><P
></P
></P
><P
><P
></P
><TABLE
BORDER="0"
><TBODY
><TR
><TD
> <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>[ ]</I
></SPAN
> - Characters enclosed in brackets will be matched if
any of the enclosed characters are encountered. For instance, <SPAN
CLASS="QUOTE"
>"[0-9]"</SPAN
>
matches any numeric digit (zero through nine). As an example, we can combine
this with <SPAN
CLASS="QUOTE"
>"+"</SPAN
> to match any digit one of more times: <SPAN
CLASS="QUOTE"
>"[0-9]+"</SPAN
>.
</TD
></TR
></TBODY
></TABLE
><P
></P
></P
><P
><P
></P
><TABLE
BORDER="0"
><TBODY
><TR
><TD
> <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>( )</I
></SPAN
> - parentheses are used to group a sub-expression,
or multiple sub-expressions.
</TD
></TR
></TBODY
></TABLE
><P
></P
></P
><P
><P
></P
><TABLE
BORDER="0"
><TBODY
><TR
><TD
> <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>|</I
></SPAN
> - The <SPAN
CLASS="QUOTE"
>"bar"</SPAN
> character works like an
<SPAN
CLASS="QUOTE"
>"or"</SPAN
> conditional statement. A match is successful if the
sub-expression on either side of <SPAN
CLASS="QUOTE"
>"|"</SPAN
> matches. As an example:
<SPAN
CLASS="QUOTE"
>"/(this|that) example/"</SPAN
> uses grouping and the bar character
and would match either <SPAN
CLASS="QUOTE"
>"this example"</SPAN
> or <SPAN
CLASS="QUOTE"
>"that
example"</SPAN
>, and nothing else.
</TD
></TR
></TBODY
></TABLE
><P
></P
></P
><P
> These are just some of the ones you are likely to use when matching URLs with
<SPAN
CLASS="APPLICATION"
>Privoxy</SPAN
>, and is a long way from a definitive
list. This is enough to get us started with a few simple examples which may
be more illuminating:</P
><P
> <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
><TT
CLASS="LITERAL"
>/.*/banners/.*</TT
></I
></SPAN
> - A simple example
that uses the common combination of <SPAN
CLASS="QUOTE"
>"."</SPAN
> and <SPAN
CLASS="QUOTE"
>"*"</SPAN
> to
denote any character, zero or more times. In other words, any string at all.
So we start with a literal forward slash, then our regular expression pattern
(<SPAN
CLASS="QUOTE"
>".*"</SPAN
>) another literal forward slash, the string
<SPAN
CLASS="QUOTE"
>"banners"</SPAN
>, another forward slash, and lastly another
<SPAN
CLASS="QUOTE"
>".*"</SPAN
>. We are building
a directory path here. This will match any file with the path that has a
directory named <SPAN
CLASS="QUOTE"
>"banners"</SPAN
> in it. The <SPAN
CLASS="QUOTE"
>".*"</SPAN
> matches
any characters, and this could conceivably be more forward slashes, so it
might expand into a much longer looking path. For example, this could match:
<SPAN
CLASS="QUOTE"
>"/eye/hate/spammers/banners/annoy_me_please.gif"</SPAN
>, or just
<SPAN
CLASS="QUOTE"
>"/banners/annoying.html"</SPAN
>, or almost an infinite number of other
possible combinations, just so it has <SPAN
CLASS="QUOTE"
>"banners"</SPAN
> in the path
somewhere.</P
><P
> And now something a little more complex:</P
><P
> <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
><TT
CLASS="LITERAL"
>/.*/adv((er)?ts?|ertis(ing|ements?))?/</TT
></I
></SPAN
> -
We have several literal forward slashes again (<SPAN
CLASS="QUOTE"
>"/"</SPAN
>), so we are
building another expression that is a file path statement. We have another
<SPAN
CLASS="QUOTE"
>".*"</SPAN
>, so we are matching against any conceivable sub-path, just so
it matches our expression. The only true literal that <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>must
match</I
></SPAN
> our pattern is <SPAN
CLASS="APPLICATION"
>adv</SPAN
>, together with
the forward slashes. What comes after the <SPAN
CLASS="QUOTE"
>"adv"</SPAN
> string is the
interesting part. </P
><P
> Remember the <SPAN
CLASS="QUOTE"
>"?"</SPAN
> means the preceding expression (either a
literal character or anything grouped with <SPAN
CLASS="QUOTE"
>"(...)"</SPAN
> in this case)
can exist or not, since this means either zero or one match. So
<SPAN
CLASS="QUOTE"
>"((er)?ts?|ertis(ing|ements?))"</SPAN
> is optional, as are the
individual sub-expressions: <SPAN
CLASS="QUOTE"
>"(er)"</SPAN
>,
<SPAN
CLASS="QUOTE"
>"(ing|ements?)"</SPAN
>, and the <SPAN
CLASS="QUOTE"
>"s"</SPAN
>. The <SPAN
CLASS="QUOTE"
>"|"</SPAN
>
means <SPAN
CLASS="QUOTE"
>"or"</SPAN
>. We have two of those. For instance,
<SPAN
CLASS="QUOTE"
>"(ing|ements?)"</SPAN
>, can expand to match either <SPAN
CLASS="QUOTE"
>"ing"</SPAN
>
<SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>OR</I
></SPAN
> <SPAN
CLASS="QUOTE"
>"ements?"</SPAN
>. What is being done here, is an
attempt at matching as many variations of <SPAN
CLASS="QUOTE"
>"advertisement"</SPAN
>, and
similar, as possible. So this would expand to match just <SPAN
CLASS="QUOTE"
>"adv"</SPAN
>,
or <SPAN
CLASS="QUOTE"
>"advert"</SPAN
>, or <SPAN
CLASS="QUOTE"
>"adverts"</SPAN
>, or
<SPAN
CLASS="QUOTE"
>"advertising"</SPAN
>, or <SPAN
CLASS="QUOTE"
>"advertisement"</SPAN
>, or
<SPAN
CLASS="QUOTE"
>"advertisements"</SPAN
>. You get the idea. But it would not match
<SPAN
CLASS="QUOTE"
>"advertizements"</SPAN
> (with a <SPAN
CLASS="QUOTE"
>"z"</SPAN
>). We could fix that by
changing our regular expression to:
<SPAN
CLASS="QUOTE"
>"/.*/adv((er)?ts?|erti(s|z)(ing|ements?))?/"</SPAN
>, which would then match
either spelling.</P
><P
> <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
><TT
CLASS="LITERAL"
>/.*/advert[0-9]+\.(gif|jpe?g)</TT
></I
></SPAN
> - Again
another path statement with forward slashes. Anything in the square brackets
<SPAN
CLASS="QUOTE"
>"[ ]"</SPAN
> can be matched. This is using <SPAN
CLASS="QUOTE"
>"0-9"</SPAN
> as a
shorthand expression to mean any digit one through nine. It is the same as
saying <SPAN
CLASS="QUOTE"
>"0123456789"</SPAN
>. So any digit matches. The <SPAN
CLASS="QUOTE"
>"+"</SPAN
>
means one or more of the preceding expression must be included. The preceding
expression here is what is in the square brackets -- in this case, any digit
one through nine. Then, at the end, we have a grouping: <SPAN
CLASS="QUOTE"
>"(gif|jpe?g)"</SPAN
>.
This includes a <SPAN
CLASS="QUOTE"
>"|"</SPAN
>, so this needs to match the expression on
either side of that bar character also. A simple <SPAN
CLASS="QUOTE"
>"gif"</SPAN
> on one side, and the other
side will in turn match either <SPAN
CLASS="QUOTE"
>"jpeg"</SPAN
> or <SPAN
CLASS="QUOTE"
>"jpg"</SPAN
>,
since the <SPAN
CLASS="QUOTE"
>"?"</SPAN
> means the letter <SPAN
CLASS="QUOTE"
>"e"</SPAN
> is optional and
can be matched once or not at all. So we are building an expression here to
match image GIF or JPEG type image file. It must include the literal
string <SPAN
CLASS="QUOTE"
>"advert"</SPAN
>, then one or more digits, and a <SPAN
CLASS="QUOTE"
>"."</SPAN
>
(which is now a literal, and not a special character, since it is escaped
with <SPAN
CLASS="QUOTE"
>"\"</SPAN
>), and lastly either <SPAN
CLASS="QUOTE"
>"gif"</SPAN
>, or
<SPAN
CLASS="QUOTE"
>"jpeg"</SPAN
>, or <SPAN
CLASS="QUOTE"
>"jpg"</SPAN
>. Some possible matches would
include: <SPAN
CLASS="QUOTE"
>"//advert1.jpg"</SPAN
>,
<SPAN
CLASS="QUOTE"
>"/nasty/ads/advert1234.gif"</SPAN
>,
<SPAN
CLASS="QUOTE"
>"/banners/from/hell/advert99.jpg"</SPAN
>. It would not match
<SPAN
CLASS="QUOTE"
>"advert1.gif"</SPAN
> (no leading slash), or
<SPAN
CLASS="QUOTE"
>"/adverts232.jpg"</SPAN
> (the expression does not include an
<SPAN
CLASS="QUOTE"
>"s"</SPAN
>), or <SPAN
CLASS="QUOTE"
>"/advert1.jsp"</SPAN
> (<SPAN
CLASS="QUOTE"
>"jsp"</SPAN
> is not
in the expression anywhere).</P
><P
> We are barely scratching the surface of regular expressions here so that you
can understand the default <SPAN
CLASS="APPLICATION"
>Privoxy</SPAN
>
configuration files, and maybe use this knowledge to customize your own
installation. There is much, much more that can be done with regular
expressions. Now that you know enough to get started, you can learn more on
your own :/</P
><P
> More reading on Perl Compatible Regular expressions:
<A
HREF="http://perldoc.perl.org/perlre.html"
TARGET="_top"
>http://perldoc.perl.org/perlre.html</A
></P
><P
> For information on regular expression based substitutions and their applications
in filters, please see the <A
HREF="filter-file.html"
>filter file tutorial</A
>
in this manual.</P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN5174"
>14.2. Privoxy's Internal Pages</A
></H2
><P
> Since <SPAN
CLASS="APPLICATION"
>Privoxy</SPAN
> proxies each requested
web page, it is easy for <SPAN
CLASS="APPLICATION"
>Privoxy</SPAN
> to
trap certain special URLs. In this way, we can talk directly to
<SPAN
CLASS="APPLICATION"
>Privoxy</SPAN
>, and see how it is
configured, see how our rules are being applied, change these
rules and other configuration options, and even turn
<SPAN
CLASS="APPLICATION"
>Privoxy's</SPAN
> filtering off, all with
a web browser.&#13;</P
><P
> The URLs listed below are the special ones that allow direct access
to <SPAN
CLASS="APPLICATION"
>Privoxy</SPAN
>. Of course,
<SPAN
CLASS="APPLICATION"
>Privoxy</SPAN
> must be running to access these. If
not, you will get a friendly error message. Internet access is not
necessary either.</P
><P
> <P
></P
><UL
><LI
><P
>
Privoxy main page:
</P
><A
NAME="AEN5188"
></A
><BLOCKQUOTE
CLASS="BLOCKQUOTE"
><P
>
<A
HREF="http://config.privoxy.org/"
TARGET="_top"
>http://config.privoxy.org/</A
>
</P
></BLOCKQUOTE
><P
> There is a shortcut: <A
HREF="http://p.p/"
TARGET="_top"
>http://p.p/</A
> (But it
doesn't provide a fall-back to a real page, in case the request is not
sent through <SPAN
CLASS="APPLICATION"
>Privoxy</SPAN
>)
</P
></LI
><LI
><P
>
Show information about the current configuration, including viewing and
editing of actions files:
</P
><A
NAME="AEN5196"
></A
><BLOCKQUOTE
CLASS="BLOCKQUOTE"
><P
>
<A
HREF="http://config.privoxy.org/show-status"
TARGET="_top"
>http://config.privoxy.org/show-status</A
>
</P
></BLOCKQUOTE
></LI
><LI
><P
>
Show the source code version numbers:
</P
><A
NAME="AEN5201"
></A
><BLOCKQUOTE
CLASS="BLOCKQUOTE"
><P
>
<A
HREF="http://config.privoxy.org/show-version"
TARGET="_top"
>http://config.privoxy.org/show-version</A
>
</P
></BLOCKQUOTE
></LI
><LI
><P
>
Show the browser's request headers:
</P
><A
NAME="AEN5206"
></A
><BLOCKQUOTE
CLASS="BLOCKQUOTE"
><P
>
<A
HREF="http://config.privoxy.org/show-request"
TARGET="_top"
>http://config.privoxy.org/show-request</A
>
</P
></BLOCKQUOTE
></LI
><LI
><P
>
Show which actions apply to a URL and why:
</P
><A
NAME="AEN5211"
></A
><BLOCKQUOTE
CLASS="BLOCKQUOTE"
><P
>
<A
HREF="http://config.privoxy.org/show-url-info"
TARGET="_top"
>http://config.privoxy.org/show-url-info</A
>
</P
></BLOCKQUOTE
></LI
><LI
><P
>
Toggle Privoxy on or off. This feature can be turned off/on in the main
<TT
CLASS="FILENAME"
>config</TT
> file. When toggled <SPAN
CLASS="QUOTE"
>"off"</SPAN
>, <SPAN
CLASS="QUOTE"
>"Privoxy"</SPAN
>
continues to run, but only as a pass-through proxy, with no actions taking
place:
</P
><A
NAME="AEN5219"
></A
><BLOCKQUOTE
CLASS="BLOCKQUOTE"
><P
>
<A
HREF="http://config.privoxy.org/toggle"
TARGET="_top"
>http://config.privoxy.org/toggle</A
>
</P
></BLOCKQUOTE
><P
> Short cuts. Turn off, then on:
</P
><A
NAME="AEN5223"
></A
><BLOCKQUOTE
CLASS="BLOCKQUOTE"
><P
>
<A
HREF="http://config.privoxy.org/toggle?set=disable"
TARGET="_top"
>http://config.privoxy.org/toggle?set=disable</A
>
</P
></BLOCKQUOTE
><A
NAME="AEN5226"
></A
><BLOCKQUOTE
CLASS="BLOCKQUOTE"
><P
>
<A
HREF="http://config.privoxy.org/toggle?set=enable"
TARGET="_top"
>http://config.privoxy.org/toggle?set=enable</A
>
</P
></BLOCKQUOTE
></LI
></UL
></P
><P
> These may be bookmarked for quick reference. See next.&#13;</P
><DIV
CLASS="SECT3"
><H3
CLASS="SECT3"
><A
NAME="BOOKMARKLETS"
>14.2.1. Bookmarklets</A
></H3
><P
> Below are some <SPAN
CLASS="QUOTE"
>"bookmarklets"</SPAN
> to allow you to easily access a
<SPAN
CLASS="QUOTE"
>"mini"</SPAN
> version of some of <SPAN
CLASS="APPLICATION"
>Privoxy's</SPAN
>
special pages. They are designed for MS Internet Explorer, but should work
equally well in Netscape, Mozilla, and other browsers which support
JavaScript. They are designed to run directly from your bookmarks - not by
clicking the links below (although that should work for testing).</P
><P
> To save them, right-click the link and choose <SPAN
CLASS="QUOTE"
>"Add to Favorites"</SPAN
>
(IE) or <SPAN
CLASS="QUOTE"
>"Add Bookmark"</SPAN
> (Netscape). You will get a warning that
the bookmark <SPAN
CLASS="QUOTE"
>"may not be safe"</SPAN
> - just click OK. Then you can run the
Bookmarklet directly from your favorites/bookmarks. For even faster access,
you can put them on the <SPAN
CLASS="QUOTE"
>"Links"</SPAN
> bar (IE) or the <SPAN
CLASS="QUOTE"
>"Personal
Toolbar"</SPAN
> (Netscape), and run them with a single click. </P
><P
> <P
></P
><UL
><LI
><P
> <A
HREF="javascript:void(window.open('http://config.privoxy.org/toggle?mini=y&#38;set=enabled','ijbstatus','width=250,height=100,resizable=yes,scrollbars=no,toolbar=no,location=no,directories=no,status=no,menubar=no,copyhistory=no').focus());"
TARGET="_top"
>Privoxy - Enable</A
>
</P
></LI
><LI
><P
> <A
HREF="javascript:void(window.open('http://config.privoxy.org/toggle?mini=y&#38;set=disabled','ijbstatus','width=250,height=100,resizable=yes,scrollbars=no,toolbar=no,location=no,directories=no,status=no,menubar=no,copyhistory=no').focus());"
TARGET="_top"
>Privoxy - Disable</A
>
</P
></LI
><LI
><P
> <A
HREF="javascript:void(window.open('http://config.privoxy.org/toggle?mini=y&#38;set=toggle','ijbstatus','width=250,height=100,resizable=yes,scrollbars=no,toolbar=no,location=no,directories=no,status=no,menubar=no,copyhistory=no').focus());"
TARGET="_top"
>Privoxy - Toggle Privoxy</A
> (Toggles between enabled and disabled)
</P
></LI
><LI
><P
> <A
HREF="javascript:void(window.open('http://config.privoxy.org/toggle?mini=y','ijbstatus','width=250,height=2,resizable=yes,scrollbars=no,toolbar=no,location=no,directories=no,status=no,menubar=no,copyhistory=no').focus());"
TARGET="_top"
>Privoxy- View Status</A
>
</P
></LI
><LI
><P
> <A
HREF="javascript:void(window.open('http://config.privoxy.org/show-url-info?url='+escape(location.href),'Why').focus());"
TARGET="_top"
>Privoxy - Why?</A
>
</P
></LI
></UL
></P
><P
> Credit: The site which gave us the general idea for these bookmarklets is
<A
HREF="http://www.bookmarklets.com/"
TARGET="_top"
>www.bookmarklets.com</A
>. They
have more information about bookmarklets. </P
></DIV
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="CHAIN"
>14.3. Chain of Events</A
></H2
><P
> Let's take a quick look at how some of <SPAN
CLASS="APPLICATION"
>Privoxy's</SPAN
>
core features are triggered, and the ensuing sequence of events when a web
page is requested by your browser:</P
><P
> <P
></P
><UL
><LI
><P
> First, your web browser requests a web page. The browser knows to send
the request to <SPAN
CLASS="APPLICATION"
>Privoxy</SPAN
>, which will in turn,
relay the request to the remote web server after passing the following
tests:
</P
></LI
><LI
><P
> <SPAN
CLASS="APPLICATION"
>Privoxy</SPAN
> traps any request for its own internal CGI
pages (e.g <A
HREF="http://p.p/"
TARGET="_top"
>http://p.p/</A
>) and sends the CGI page back to the browser.
</P
></LI
><LI
><P
> Next, <SPAN
CLASS="APPLICATION"
>Privoxy</SPAN
> checks to see if the URL
matches any <A
HREF="actions-file.html#BLOCK"
><SPAN
CLASS="QUOTE"
>"+block"</SPAN
></A
> patterns. If
so, the URL is then blocked, and the remote web server will not be contacted.
<A
HREF="actions-file.html#HANDLE-AS-IMAGE"
><SPAN
CLASS="QUOTE"
>"+handle-as-image"</SPAN
></A
>
and
<A
HREF="actions-file.html#HANDLE-AS-EMPTY-DOCUMENT"
><SPAN
CLASS="QUOTE"
>"+handle-as-empty-document"</SPAN
></A
>
are then checked, and if there is no match, an
HTML <SPAN
CLASS="QUOTE"
>"BLOCKED"</SPAN
> page is sent back to the browser. Otherwise, if
it does match, an image is returned for the former, and an empty text
document for the latter. The type of image would depend on the setting of
<A
HREF="actions-file.html#SET-IMAGE-BLOCKER"
><SPAN
CLASS="QUOTE"
>"+set-image-blocker"</SPAN
></A
>
(blank, checkerboard pattern, or an HTTP redirect to an image elsewhere).
</P
></LI
><LI
><P
> Untrusted URLs are blocked. If URLs are being added to the
<TT
CLASS="FILENAME"
>trust</TT
> file, then that is done.
</P
></LI
><LI
><P
> If the URL pattern matches the <A
HREF="actions-file.html#FAST-REDIRECTS"
><SPAN
CLASS="QUOTE"
>"+fast-redirects"</SPAN
></A
> action,
it is then processed. Unwanted parts of the requested URL are stripped.
</P
></LI
><LI
><P
> Now the rest of the client browser's request headers are processed. If any
of these match any of the relevant actions (e.g. <A
HREF="actions-file.html#HIDE-USER-AGENT"
><SPAN
CLASS="QUOTE"
>"+hide-user-agent"</SPAN
></A
>,
etc.), headers are suppressed or forged as determined by these actions and
their parameters.
</P
></LI
><LI
><P
> Now the web server starts sending its response back (i.e. typically a web
page).
</P
></LI
><LI
><P
> First, the server headers are read and processed to determine, among other
things, the MIME type (document type) and encoding. The headers are then
filtered as determined by the
<A
HREF="actions-file.html#CRUNCH-INCOMING-COOKIES"
><SPAN
CLASS="QUOTE"
>"+crunch-incoming-cookies"</SPAN
></A
>,
<A
HREF="actions-file.html#SESSION-COOKIES-ONLY"
><SPAN
CLASS="QUOTE"
>"+session-cookies-only"</SPAN
></A
>,
and <A
HREF="actions-file.html#DOWNGRADE-HTTP-VERSION"
><SPAN
CLASS="QUOTE"
>"+downgrade-http-version"</SPAN
></A
>
actions.
</P
></LI
><LI
><P
> If any <A
HREF="actions-file.html#FILTER"
><SPAN
CLASS="QUOTE"
>"+filter"</SPAN
></A
> action
or <A
HREF="actions-file.html#DEANIMATE-GIFS"
><SPAN
CLASS="QUOTE"
>"+deanimate-gifs"</SPAN
></A
>
action applies (and the document type fits the action), the rest of the page is
read into memory (up to a configurable limit). Then the filter rules (from
<TT
CLASS="FILENAME"
>default.filter</TT
> and any other filter files) are
processed against the buffered content. Filters are applied in the order
they are specified in one of the filter files. Animated GIFs, if present,
are reduced to either the first or last frame, depending on the action
setting.The entire page, which is now filtered, is then sent by
<SPAN
CLASS="APPLICATION"
>Privoxy</SPAN
> back to your browser.
</P
><P
> If neither a <A
HREF="actions-file.html#FILTER"
><SPAN
CLASS="QUOTE"
>"+filter"</SPAN
></A
> action
or <A
HREF="actions-file.html#DEANIMATE-GIFS"
><SPAN
CLASS="QUOTE"
>"+deanimate-gifs"</SPAN
></A
>
matches, then <SPAN
CLASS="APPLICATION"
>Privoxy</SPAN
> passes the raw data through
to the client browser as it becomes available.
</P
></LI
><LI
><P
> As the browser receives the now (possibly filtered) page content, it
reads and then requests any URLs that may be embedded within the page
source, e.g. ad images, stylesheets, JavaScript, other HTML documents (e.g.
frames), sounds, etc. For each of these objects, the browser issues a
separate request (this is easily viewable in <SPAN
CLASS="APPLICATION"
>Privoxy's</SPAN
>
logs). And each such request is in turn processed just as above. Note that a
complex web page will have many, many such embedded URLs. If these
secondary requests are to a different server, then quite possibly a very
differing set of actions is triggered.
</P
></LI
></UL
></P
><P
> NOTE: This is somewhat of a simplistic overview of what happens with each URL
request. For the sake of brevity and simplicity, we have focused on
<SPAN
CLASS="APPLICATION"
>Privoxy's</SPAN
> core features only.</P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="ACTIONSANAT"
>14.4. Troubleshooting: Anatomy of an Action</A
></H2
><P
> The way <SPAN
CLASS="APPLICATION"
>Privoxy</SPAN
> applies
<A
HREF="actions-file.html#ACTIONS"
>actions</A
> and <A
HREF="actions-file.html#FILTER"
>filters</A
>
to any given URL can be complex, and not always so
easy to understand what is happening. And sometimes we need to be able to
<SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>see</I
></SPAN
> just what <SPAN
CLASS="APPLICATION"
>Privoxy</SPAN
> is
doing. Especially, if something <SPAN
CLASS="APPLICATION"
>Privoxy</SPAN
> is doing
is causing us a problem inadvertently. It can be a little daunting to look at
the actions and filters files themselves, since they tend to be filled with
<A
HREF="appendix.html#REGEX"
>regular expressions</A
> whose consequences are not
always so obvious. </P
><P
> One quick test to see if <SPAN
CLASS="APPLICATION"
>Privoxy</SPAN
> is causing a problem
or not, is to disable it temporarily. This should be the first troubleshooting
step. See <A
HREF="appendix.html#BOOKMARKLETS"
>the Bookmarklets</A
> section on a quick
and easy way to do this (be sure to flush caches afterward!). Looking at the
logs is a good idea too. (Note that both the toggle feature and logging are
enabled via <TT
CLASS="FILENAME"
>config</TT
> file settings, and may need to be
turned <SPAN
CLASS="QUOTE"
>"on"</SPAN
>.)</P
><P
> Another easy troubleshooting step to try is if you have done any
customization of your installation, revert back to the installed
defaults and see if that helps. There are times the developers get complaints
about one thing or another, and the problem is more related to a customized
configuration issue.</P
><P
> <SPAN
CLASS="APPLICATION"
>Privoxy</SPAN
> also provides the
<A
HREF="http://config.privoxy.org/show-url-info"
TARGET="_top"
>http://config.privoxy.org/show-url-info</A
>
page that can show us very specifically how <SPAN
CLASS="APPLICATION"
>actions</SPAN
>
are being applied to any given URL. This is a big help for troubleshooting.</P
><P
> First, enter one URL (or partial URL) at the prompt, and then
<SPAN
CLASS="APPLICATION"
>Privoxy</SPAN
> will tell us
how the current configuration will handle it. This will not
help with filtering effects (i.e. the <A
HREF="actions-file.html#FILTER"
><SPAN
CLASS="QUOTE"
>"+filter"</SPAN
></A
> action) from
one of the filter files since this is handled very
differently and not so easy to trap! It also will not tell you about any other
URLs that may be embedded within the URL you are testing. For instance, images
such as ads are expressed as URLs within the raw page source of HTML pages. So
you will only get info for the actual URL that is pasted into the prompt area
-- not any sub-URLs. If you want to know about embedded URLs like ads, you
will have to dig those out of the HTML source. Use your browser's <SPAN
CLASS="QUOTE"
>"View
Page Source"</SPAN
> option for this. Or right click on the ad, and grab the
URL.</P
><P
> Let's try an example, <A
HREF="http://google.com"
TARGET="_top"
>google.com</A
>,
and look at it one section at a time in a sample configuration (your real
configuration may vary):</P
><P
> <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="SCREEN"
> Matches for http://www.google.com:
In file: default.action <SPAN
CLASS="GUIBUTTON"
>[ View ]</SPAN
> <SPAN
CLASS="GUIBUTTON"
>[ Edit ]</SPAN
>
{+change-x-forwarded-for{block}
+deanimate-gifs {last}
+fast-redirects {check-decoded-url}
+filter {refresh-tags}
+filter {img-reorder}
+filter {banners-by-size}
+filter {webbugs}
+filter {jumping-windows}
+filter {ie-exploits}
+hide-from-header {block}
+hide-referrer {forge}
+session-cookies-only
+set-image-blocker {pattern}
/
{ -session-cookies-only }
.google.com
{ -fast-redirects }
.google.com
In file: user.action <SPAN
CLASS="GUIBUTTON"
>[ View ]</SPAN
> <SPAN
CLASS="GUIBUTTON"
>[ Edit ]</SPAN
>
(no matches in this file) </PRE
></TD
></TR
></TABLE
></P
><P
> This is telling us how we have defined our
<A
HREF="actions-file.html#ACTIONS"
><SPAN
CLASS="QUOTE"
>"actions"</SPAN
></A
>, and
which ones match for our test case, <SPAN
CLASS="QUOTE"
>"google.com"</SPAN
>.
Displayed is all the actions that are available to us. Remember,
the <TT
CLASS="LITERAL"
>+</TT
> sign denotes <SPAN
CLASS="QUOTE"
>"on"</SPAN
>. <TT
CLASS="LITERAL"
>-</TT
>
denotes <SPAN
CLASS="QUOTE"
>"off"</SPAN
>. So some are <SPAN
CLASS="QUOTE"
>"on"</SPAN
> here, but many
are <SPAN
CLASS="QUOTE"
>"off"</SPAN
>. Each example we try may provide a slightly different
end result, depending on our configuration directives.</P
><P
> The first listing
is for our <TT
CLASS="FILENAME"
>default.action</TT
> file. The large, multi-line
listing, is how the actions are set to match for all URLs, i.e. our default
settings. If you look at your <SPAN
CLASS="QUOTE"
>"actions"</SPAN
> file, this would be the
section just below the <SPAN
CLASS="QUOTE"
>"aliases"</SPAN
> section near the top. This
will apply to all URLs as signified by the single forward slash at the end
of the listing -- <SPAN
CLASS="QUOTE"
>" / "</SPAN
>.</P
><P
> But we have defined additional actions that would be exceptions to these general
rules, and then we list specific URLs (or patterns) that these exceptions
would apply to. Last match wins. Just below this then are two explicit
matches for <SPAN
CLASS="QUOTE"
>".google.com"</SPAN
>. The first is negating our previous
cookie setting, which was for <A
HREF="actions-file.html#SESSION-COOKIES-ONLY"
><SPAN
CLASS="QUOTE"
>"+session-cookies-only"</SPAN
></A
>
(i.e. not persistent). So we will allow persistent cookies for google, at
least that is how it is in this example. The second turns
<SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>off</I
></SPAN
> any <A
HREF="actions-file.html#FAST-REDIRECTS"
><SPAN
CLASS="QUOTE"
>"+fast-redirects"</SPAN
></A
>
action, allowing this to take place unmolested. Note that there is a leading
dot here -- <SPAN
CLASS="QUOTE"
>".google.com"</SPAN
>. This will match any hosts and
sub-domains, in the google.com domain also, such as
<SPAN
CLASS="QUOTE"
>"www.google.com"</SPAN
> or <SPAN
CLASS="QUOTE"
>"mail.google.com"</SPAN
>. But it would not
match <SPAN
CLASS="QUOTE"
>"www.google.de"</SPAN
>! So, apparently, we have these two actions
defined as exceptions to the general rules at the top somewhere in the lower
part of our <TT
CLASS="FILENAME"
>default.action</TT
> file, and
<SPAN
CLASS="QUOTE"
>"google.com"</SPAN
> is referenced somewhere in these latter sections.</P
><P
> Then, for our <TT
CLASS="FILENAME"
>user.action</TT
> file, we again have no hits.
So there is nothing google-specific that we might have added to our own, local
configuration. If there was, those actions would over-rule any actions from
previously processed files, such as <TT
CLASS="FILENAME"
>default.action</TT
>.
<TT
CLASS="FILENAME"
>user.action</TT
> typically has the last word. This is the
best place to put hard and fast exceptions,</P
><P
> And finally we pull it all together in the bottom section and summarize how
<SPAN
CLASS="APPLICATION"
>Privoxy</SPAN
> is applying all its <SPAN
CLASS="QUOTE"
>"actions"</SPAN
>
to <SPAN
CLASS="QUOTE"
>"google.com"</SPAN
>:&#13;</P
><P
> <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="SCREEN"
>&#13; Final results:
-add-header
-block
+change-x-forwarded-for{block}
-client-header-filter{hide-tor-exit-notation}
-content-type-overwrite
-crunch-client-header
-crunch-if-none-match
-crunch-incoming-cookies
-crunch-outgoing-cookies
-crunch-server-header
+deanimate-gifs {last}
-downgrade-http-version
-fast-redirects
-filter {js-events}
-filter {content-cookies}
-filter {all-popups}
-filter {banners-by-link}
-filter {tiny-textforms}
-filter {frameset-borders}
-filter {demoronizer}
-filter {shockwave-flash}
-filter {quicktime-kioskmode}
-filter {fun}
-filter {crude-parental}
-filter {site-specifics}
-filter {js-annoyances}
-filter {html-annoyances}
+filter {refresh-tags}
-filter {unsolicited-popups}
+filter {img-reorder}
+filter {banners-by-size}
+filter {webbugs}
+filter {jumping-windows}
+filter {ie-exploits}
-filter {google}
-filter {yahoo}
-filter {msn}
-filter {blogspot}
-filter {no-ping}
-force-text-mode
-handle-as-empty-document
-handle-as-image
-hide-accept-language
-hide-content-disposition
+hide-from-header {block}
-hide-if-modified-since
+hide-referrer {forge}
-hide-user-agent
-limit-connect
-overwrite-last-modified
-prevent-compression
-redirect
-server-header-filter{xml-to-html}
-server-header-filter{html-to-xml}
-session-cookies-only
+set-image-blocker {pattern} </PRE
></TD
></TR
></TABLE
></P
><P
> Notice the only difference here to the previous listing, is to
<SPAN
CLASS="QUOTE"
>"fast-redirects"</SPAN
> and <SPAN
CLASS="QUOTE"
>"session-cookies-only"</SPAN
>,
which are activated specifically for this site in our configuration,
and thus show in the <SPAN
CLASS="QUOTE"
>"Final Results"</SPAN
>.</P
><P
> Now another example, <SPAN
CLASS="QUOTE"
>"ad.doubleclick.net"</SPAN
>:</P
><P
> <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="SCREEN"
>&#13; { +block{Domains starts with "ad"} }
ad*.
{ +block{Domain contains "ad"} }
.ad.
{ +block{Doubleclick banner server} +handle-as-image }
.[a-vx-z]*.doubleclick.net</PRE
></TD
></TR
></TABLE
></P
><P
> We'll just show the interesting part here - the explicit matches. It is
matched three different times. Two <SPAN
CLASS="QUOTE"
>"+block{}"</SPAN
> sections,
and a <SPAN
CLASS="QUOTE"
>"+block{} +handle-as-image"</SPAN
>,
which is the expanded form of one of our aliases that had been defined as:
<SPAN
CLASS="QUOTE"
>"+block-as-image"</SPAN
>. (<A
HREF="actions-file.html#ALIASES"
><SPAN
CLASS="QUOTE"
>"Aliases"</SPAN
></A
> are defined in
the first section of the actions file and typically used to combine more
than one action.)</P
><P
> Any one of these would have done the trick and blocked this as an unwanted
image. This is unnecessarily redundant since the last case effectively
would also cover the first. No point in taking chances with these guys
though ;-) Note that if you want an ad or obnoxious
URL to be invisible, it should be defined as <SPAN
CLASS="QUOTE"
>"ad.doubleclick.net"</SPAN
>
is done here -- as both a <A
HREF="actions-file.html#BLOCK"
><SPAN
CLASS="QUOTE"
>"+block{}"</SPAN
></A
>
<SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>and</I
></SPAN
> an
<A
HREF="actions-file.html#HANDLE-AS-IMAGE"
><SPAN
CLASS="QUOTE"
>"+handle-as-image"</SPAN
></A
>.
The custom alias <SPAN
CLASS="QUOTE"
>"<TT
CLASS="LITERAL"
>+block-as-image</TT
>"</SPAN
> just
simplifies the process and make it more readable.</P
><P
> One last example. Let's try <SPAN
CLASS="QUOTE"
>"http://www.example.net/adsl/HOWTO/"</SPAN
>.
This one is giving us problems. We are getting a blank page. Hmmm ...</P
><P
> <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="SCREEN"
>&#13; Matches for http://www.example.net/adsl/HOWTO/:
In file: default.action <SPAN
CLASS="GUIBUTTON"
>[ View ]</SPAN
> <SPAN
CLASS="GUIBUTTON"
>[ Edit ]</SPAN
>
{-add-header
-block
+change-x-forwarded-for{block}
-client-header-filter{hide-tor-exit-notation}
-content-type-overwrite
-crunch-client-header
-crunch-if-none-match
-crunch-incoming-cookies
-crunch-outgoing-cookies
-crunch-server-header
+deanimate-gifs
-downgrade-http-version
+fast-redirects {check-decoded-url}
-filter {js-events}
-filter {content-cookies}
-filter {all-popups}
-filter {banners-by-link}
-filter {tiny-textforms}
-filter {frameset-borders}
-filter {demoronizer}
-filter {shockwave-flash}
-filter {quicktime-kioskmode}
-filter {fun}
-filter {crude-parental}
-filter {site-specifics}
-filter {js-annoyances}
-filter {html-annoyances}
+filter {refresh-tags}
-filter {unsolicited-popups}
+filter {img-reorder}
+filter {banners-by-size}
+filter {webbugs}
+filter {jumping-windows}
+filter {ie-exploits}
-filter {google}
-filter {yahoo}
-filter {msn}
-filter {blogspot}
-filter {no-ping}
-force-text-mode
-handle-as-empty-document
-handle-as-image
-hide-accept-language
-hide-content-disposition
+hide-from-header{block}
+hide-referer{forge}
-hide-user-agent
-overwrite-last-modified
+prevent-compression
-redirect
-server-header-filter{xml-to-html}
-server-header-filter{html-to-xml}
+session-cookies-only
+set-image-blocker{blank} }
/
{ +block{Path contains "ads".} +handle-as-image }
/ads</PRE
></TD
></TR
></TABLE
></P
><P
> Ooops, the <SPAN
CLASS="QUOTE"
>"/adsl/"</SPAN
> is matching <SPAN
CLASS="QUOTE"
>"/ads"</SPAN
> in our
configuration! But we did not want this at all! Now we see why we get the
blank page. It is actually triggering two different actions here, and
the effects are aggregated so that the URL is blocked, and <SPAN
CLASS="APPLICATION"
>Privoxy</SPAN
> is told
to treat the block as if it were an image. But this is, of course, all wrong.
We could now add a new action below this (or better in our own
<TT
CLASS="FILENAME"
>user.action</TT
> file) that explicitly
<SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>un</I
></SPAN
> blocks (
<A
HREF="actions-file.html#BLOCK"
><SPAN
CLASS="QUOTE"
>"{-block}"</SPAN
></A
>) paths with
<SPAN
CLASS="QUOTE"
>"adsl"</SPAN
> in them (remember, last match in the configuration
wins). There are various ways to handle such exceptions. Example:</P
><P
> <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="SCREEN"
>&#13; { -block }
/adsl</PRE
></TD
></TR
></TABLE
></P
><P
> Now the page displays ;-)
Remember to flush your browser's caches when making these kinds of changes to
your configuration to insure that you get a freshly delivered page! Or, try
using <TT
CLASS="LITERAL"
>Shift+Reload</TT
>.</P
><P
> But now what about a situation where we get no explicit matches like
we did with:</P
><P
> <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="SCREEN"
>&#13; { +block{Path starts with "ads".} +handle-as-image }
/ads</PRE
></TD
></TR
></TABLE
></P
><P
> That actually was very helpful and pointed us quickly to where the problem
was. If you don't get this kind of match, then it means one of the default
rules in the first section of <TT
CLASS="FILENAME"
>default.action</TT
> is causing
the problem. This would require some guesswork, and maybe a little trial and
error to isolate the offending rule. One likely cause would be one of the
<A
HREF="actions-file.html#FILTER"
><SPAN
CLASS="QUOTE"
>"+filter"</SPAN
></A
> actions.
These tend to be harder to troubleshoot.
Try adding the URL for the site to one of aliases that turn off
<A
HREF="actions-file.html#FILTER"
><SPAN
CLASS="QUOTE"
>"+filter"</SPAN
></A
>:</P
><P
> <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="SCREEN"
>&#13; { shop }
.quietpc.com
.worldpay.com # for quietpc.com
.jungle.com
.scan.co.uk
.forbes.com</PRE
></TD
></TR
></TABLE
></P
><P
> <SPAN
CLASS="QUOTE"
>"<TT
CLASS="LITERAL"
>{ shop }</TT
>"</SPAN
> is an <SPAN
CLASS="QUOTE"
>"alias"</SPAN
> that expands to
<SPAN
CLASS="QUOTE"
>"<TT
CLASS="LITERAL"
>{ -filter -session-cookies-only }</TT
>"</SPAN
>.
Or you could do your own exception to negate filtering:&#13;</P
><P
> <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="SCREEN"
>&#13; { -filter }
# Disable ALL filter actions for sites in this section
.forbes.com
developer.ibm.com
localhost</PRE
></TD
></TR
></TABLE
></P
><P
> This would turn off all filtering for these sites. This is best
put in <TT
CLASS="FILENAME"
>user.action</TT
>, for local site
exceptions. Note that when a simple domain pattern is used by itself (without
the subsequent path portion), all sub-pages within that domain are included
automatically in the scope of the action.</P
><P
> Images that are inexplicably being blocked, may well be hitting the
<A
HREF="actions-file.html#FILTER-BANNERS-BY-SIZE"
><SPAN
CLASS="QUOTE"
>"+filter{banners-by-size}"</SPAN
></A
>
rule, which assumes
that images of certain sizes are ad banners (works well
<SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>most of the time</I
></SPAN
> since these tend to be standardized).</P
><P
> <SPAN
CLASS="QUOTE"
>"<TT
CLASS="LITERAL"
>{ fragile }</TT
>"</SPAN
> is an alias that disables most
actions that are the most likely to cause trouble. This can be used as a
last resort for problem sites. </P
><P
> <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="SCREEN"
>&#13; { fragile }
# Handle with care: easy to break
mail.google.
mybank.example.com</PRE
></TD
></TR
></TABLE
></P
><P
> <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>Remember to flush caches!</I
></SPAN
> Note that the
<TT
CLASS="LITERAL"
>mail.google</TT
> reference lacks the TLD portion (e.g.
<SPAN
CLASS="QUOTE"
>".com"</SPAN
>). This will effectively match any TLD with
<TT
CLASS="LITERAL"
>google</TT
> in it, such as <TT
CLASS="LITERAL"
>mail.google.de.</TT
>,
just as an example.</P
><P
>
If this still does not work, you will have to go through the remaining
actions one by one to find which one(s) is causing the problem.</P
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