I won't ask why you've explicitly asked for the library to be in C, rather than C++
It hardly seems important. You're obviously after something that 'just works', rather than an understanding of the underlying algorithms. Besides, unless you like to do it for pleasure, there's not much point in re-inventing the wheel.
Though your Google-searching skills leave something to be desired
Try this on for size:
http://www.netsurf-browser.org/projects/libcss/[
^]