This question is best asked in the legal section. Have you checked it out?.
But to answer your question, yes. It'll depend mainly on how similarly-used or.
Relatedely-used the name is to any potential trademark holder out there...
Your question isn't clear. Please elaborate, and explain how you would use your site..
Also, moved to the proper forum (Thanks, Dave )..
I would say it highly depends on the TM, if the word could be used as anything else, and how popular and known the word is.
For example: if the word was sonyfinder.com, it's pretty clear it isn't generic in any way and the common person would know exactly what it was putting you on shakey ground TM-wise. However, if it was Palmfinder, you might have some room to argue, since palm is not only a handheld computer, but a part of your hand and a tree. However, even in this case, it would be more how you use and market it that determined wether the TM owner had a case against you...
Ok let say my site is xtremefinder.com I'm using the site to find a lets say a dating site, but the other site name is extremfinder.com. Extremfinder.com is not in the US it's in china and both of the sites are use for the same purpose is this a violation of trademark? No I didnt know there was a legal section to this site.
Oh I forgot this site that in china dont have a trademark in the US..
Your example has both version being different than the generic word "extreme", therefore, both are typos an one is presumably TM'd. Many people do get by with different typo spellings like this without a problem. However, I don't deal with them myself. The keyword in UDRP cases is "confusingly similar". In other words, are you trying to confuse their users with your name, or profit from their work of making their site popular and a known name...