I'm trying to use a .htaccess file to prevent people being sent to the default site on the raq.

currently if you go to badsite.domain.com it will send you to servername.domain.com

I really want it to go to www.domain.com (http://www.domain.com)

The box only hosts 1 domain but several sub domains, I don't want to rename the server just for this and would prefer to have www. as a virtual site
I've tried redirect, rewrite all kinds of variations but everything just makes the raq respond

Internal Server Error

The server encountered an internal error or misconfiguration and was unable to complete your request.

I can' find any info on the customised RAQ .htaccess format/commands just lots of people making references to it...
Anyone know where it's documented please?