diff --git a/docs/_docs/extras.md b/docs/_docs/extras.md
index 87971f74..e79b9e90 100644
--- a/docs/_docs/extras.md
+++ b/docs/_docs/extras.md
@@ -6,6 +6,16 @@ permalink: /docs/extras/
 There are a number of (optional) extra features that Jekyll supports that you
 may want to install, depending on how you plan to use Jekyll.
 
+## Web Highlights and Commenting 
+
+Register your site with [txtpen](https://txtpen.com). Then append 
+
+```html
+    <script src="https://txtpen.com/embed.js?site=<your site name>" />
+```
+
+to your template files in `/_layout` folder.
+
 ## Math Support
 
 Kramdown comes with optional support for LaTeX to PNG rendering via [MathJax](https://www.mathjax.org) within math blocks. See the Kramdown documentation on [math blocks](http://kramdown.gettalong.org/syntax.html#math-blocks) and [math support](http://kramdown.gettalong.org/converter/html.html#math-support) for more details. MathJax requires you to include JavaScript or CSS to render the LaTeX, e.g.