problem in posting and reply in SMF

[gomcodoctor]

Hi!
Whenever I want to post link or any URL in any topic or reply to any of the post then I got this error.

"An appropriate representation of the requested resource /index.php could not be found on this server"

But posting of simple text is working well.

I am using intermediate version of PHP

Also I want to use Search engine friendly URLsApache only! but it show This feature will not work on your server.

Please help me.

Thanks a lot

[Christopher]

Moved to scripts and 3rd party apps

[TheMan177]

What is the contents of your .htaccess file in that directory?