RewriteRule Help for htaccess file

[tomjung]

I am a complete newb to the RewriteRule so I'm asking for some help here. I have a website that I want to make replicated.

When someone signs up to the site they create their own replicated site, For example: mydomain.com/TheirWebsiteName

So when someone comes to their url: mydomain.com/TheirWebsiteName I want my server to process that as mydomain.com/index.php?aid=TheirWebsiteName

Can anyone help me out with this one?

(not sure if this is in the write place, everything looks to be in german)