The standard you're looking for ISO/IEC 9899 available from ISO for the low low price of 352 Swiss Francs. I like to have the standard around, it pays to have the authoritative version especially when doing cross-compiler work. Whatever you do, don't Google for C99.pdf as that might find you bootlegged copies.
For reference I like to refer to Open Group's POSIX standard which also lets you know what's a POSIX extension and what's ISO C99.