Searching for "C standard doc" does not actually work.
"C99 standard doc" let's you find http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1124.pdf but searching for "function declaration" does not take you anywhere useful.
That's not to say reading the whole thing is a waste of time, just beyond the scope of most new programmers.
But it's way easier to consult the lazyweb than to do your own research.