mod rewrites for search engine friendly URLs

On a Linux web hosting account this works great:

Open a text editor (Notepad)

Paste this into the file:

RewriteEngine On
RewriteRule ^app/([A-Za-z0-9_-]+)$ index.php?app=$1 [L]

Save the file as .htaccess

Upload it.

That's all there is to it.

Reference:
http://www.sourcerally.net/Scripts/42-Web---Root-Directory