I don't notice any strange behaviour, and I looked at the page with Mozilla and Internet Explorer. Also, it does not look like a virus to me, but just like a login window for MSN Communities
Indeed, it seems to be just an image in The Napster's signature. This image is hosted on MSN Communities (German site, therefore .de), and you have to sign in to see the image. Therefore, that window pops up. Nothing dangerous, I'd say