Sorry if this is a rather elementary question, however when I'm looking at my AdSense account, in particular "top sites" I often have my main website listed as www.domain.com, and also domain.com. It must've been the way I set it up originally. Not quite sure why it's doing it. I normally see the domain with the www in front of it. If anyone can shed some light on this, I can make some changes so I just see the one domain listed, instead of both of them.