Summary: The comments in prettify.js are authoritative but the lexer should work on a number of languages including C and friends, Java, Python, Bash, SQL, HTML, XML, CSS, Javascript, and Makefiles. It works passably on Ruby, PHP, VB, and Awk and a decent subset of Perl and Ruby, but, because of commenting conventions, doesn't work on Smalltalk, or CAML-like languages.
See more:
http://google-code-prettify.googlecode.com/svn/trunk/README.html