how to prefix "blog." in front of domain name? the goal is to have => blog.mysite.com

[eluser]tim peterson[/eluser]
can someone help me understand how i can prefix a word to my domain name in codeigniter.

I'd like to add something like "blog." in front of mysite.com to make blog.mysite.com.

If this is an htaccess issue, can you show what that code would look like?

thank you,
tim