So you've run up against an empty page in the WordPress Codex's Function Reference. Where do you turn? Here are some sites that may help you in your search for answers.
Improving the Codex
Because the Codex is a community-edited wiki,
anyone with a WordPress.org ID can add pages
to the Codex. So, once I have a clear idea how
wp_max_upload_size() works, I can add that
info to the Codex. (I haven't yet. But I should.)
References &c
● Photos (CC-licensed):
– “This is where the sidewalk ends...” by Marissa Garza
http://www.flickr.com/photos/marzbars/3688823218/
– “Mark Cries in the Fetal Position” by Jared Cherup
http://www.flickr.com/photos/jarbo/2612243/
● http://wordpress.stackexchange.com/
● http://wpseek.com/
● http://queryposts.com/
● And of course http://codex.wordpress.org/