mod_rewrite taking over all the links on the page

Answer 1

You need to make your links relative to the root, like so:

<a href="/send_message.php">link</a>

Note the slash before send_message.php.

Answer 2

I personally only see one solution: Just make all your links absolute. It's not directly a problem with mod_rewrite, but the browsers way of interpreting these links. From their perspective you have a directory structure and they interpret the relative position accordingly.

Answer 3

Other solutions include a BASE href or just rewriting all the page elements that can be referenced by the imaginary context root you're showing the client.