Pygments, a Python-based code highlighting tool, comes with a set of builtin styles (not css files) for code highlighting. You have to generate a CSS file using the command line. You can generate these yourself, but this git repository has already generated them for you.
These css files were generated using pygmentize on the command line like so:
pygmentize -S default -f html -a .highlight > default.css
You can remove or change the top-level class by removing or modifying -a .highlight in the makefile.
To regenerate them all with whichever pygments version you are using, run:
cd pygments-css make cssfiles