Hyphens and underscores
 

Another noob question. I want to have a main page for the forum however prior to creating the forum I never thought about looking up other sites with the same domain name. Of course mine has been used. I don't want to have a different name as this can confuse others, so if I am registering a domain name can I use a hyphens?

If you are unsure, just type it in. They will instruct you whether or not you are using the correct format for the domain name

Hyphens are always better for url structure. google will treat an underscore as part of the word while hyphens are treated like spaces. example: compare the results for a search for poker_sites and poker-sites