I've just noticed (twice) the following ad text ブルース・カントリー I don't know if it's a foreign language thing but do know it looks very odd on my site and I would have thought it would have failed validation. I never followed the link so don't know the destination page.
Your site isn't set up to display the characters correctly so its defaulting to gibberish. It is most likely a valid site.
This thread is the place to start: http://forums.digitalpoint.com/showthread.php?t=6420 then search from there. It has to do with the type of coding you specify on your site.