Mod rewrite
From GregariusWiki
Mod_rewrite is an Apache module that turns ugly URL's with lots of questions marks and ampersands into sexy url's that are easy to remember. Unfortunately, not all servers have support for mod_rewrite. Gregarius runs perfectly fine without mod_rewrite. Just make sure that you remove the .htaccess file in your gregarius directory and turn rss.output.usemodrewrite off in your Administration configuration.

