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.
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