What do you mean 'the default homepage'? Are you seeing your blog with the cutom skin instead of the one you chose? You might want to disable skin switching. Your browser may have a cookie that says you want to view the site with the custom skin. This overrides the default skin in the backoffice if you allow skin switching. I usually don't allow skin switching.

Look at this page:
http://atennisblog.com/federerphile/
There is a message on there that says: "Welcome to b2evolution
This is the default homepage for b2evolution. It will be displayed as long as you don't select a default blog in the general settings."

Well, I have chosen a default blog in my general settings page. It doesn't pull up whether I allow skin switching or not.

Please help!

Ok, I see. Try this. Go to the Blogs tab in the backoffice. Select your main blog (the one you want to appear at the url you gave me). Under 'Preferred access type:' choose 'Default blog on index.php' and save.

That worked! Thanks very much. You're a genious :D