This is not uncommon—unfortunately. What could be happening is that your site is being “spoofed” by someone who wants to drive traffic to his or her web site. If you feel your site is indeed being spoofed, copy the suspect web site URLs and send to the company that is hosting your web site. They will help resolve the problem. To avoid this in the future, sometimes it makes sense to register all versions of your domain name (e.g. your web site name at “.com” or “.net” or “.biz”).