prettify.js. a Javascript module; jsbeautifier.org. syntax highlighting of source code snippets in an html page.

http://code.google.com/p/google-code-prettify/
For an example, see the README: http://google-code-prettify.googlecode.com/svn/trunk/README.html

Download: http://code.google.com/p/google-code-prettify/downloads/list
chrome extension:
https://chrome.google.com/webstore/detail/piekbefgpgdecckjcpffhnacjflfoddg?hl=fr#

for other browsers: http://jsbeautifier.org/


Features:

• Works on HTML pages
• Works even if code contains embedded links, line numbers, etc.
• Simple API : include some JS&CSS and add an onload handler.
• Lightweights : small download and does not block page from loading while running.
• Customizable styles via CSS.
  See the themes gallery (gallery of themes for code prettify):
  http://google-code-prettify.googlecode.com/svn/trunk/styles/index.html
• Supports all C-like, Bash-like, and XML-like languages. No need to specify the language.
• Extensible language handlers for other languages. You can specify the language.
• Widely used with good cross-browser support. 
• Powers code.google.com and stackoverflow.com