Read this manual if you’re not sure about enabling Clean URL for your brand new Drupal installation. Or simply create a .htaccess and add the following lines of code. That’s it. If you’re working with Drupal 6.x it automatically detects CleanURL’s working. enjoy!

RewriteEngine on
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php?q=$1 [L,QSA]