RewriteRule

Welcome

I need rewrite any URL address to http://example/index.php. For example:

http://example/foo/bar
or
http://example/foo/bar/foo2/bar2

I want rewrite to
http://example/index.php

But NOT pictures and CSS. Pictures (gif, jpeg, png) are stored in
/home/user/public_html/site/pictures and subdirectories.
CSS are stored in /home/user/public_html/site/CSS.

I find this:
RewriteRule ^/(css)/(.*)$ /home/user/public_html/site/CSS$2 [l]
RewriteRule !^/(css)/.*$ /home/user/public_html/site/index.php [l]
but it isn't work:-(

Can you help me write properly RewriteRule?

Thank you,
Marcin