Anyone can tell me that someone is giving me the nofollow back links from his site then its beneficial for my site or not.
Okay... 1.) It is an attribute, not a tag. Tags are enclosed by opening and closing brackets, like so: <tag> - most HTML "elements" (the main part of the tag, such as "body" or "div") have an opening and closing tag, like <div> and </div> 2.) It depends on how the attribute is being used. If you are using it to tell Google that the affiliate link pointing to Shady Eddy's Bail Bonds' latest white paper on proper conduct in a court room (available for $29.95) is not the one they are looking for (like the old Jedi Mind Trick - "these are not the droids you are looking for; move along"), then yes. It would be beneficial for your site. However, if you were to leave a comment on another site and the link had the attribute added to it, then you would see absolutely no benefit whatsoever since as far as Google is concerned it would not exist (Yahoo! is a different story, however).
if that site has large traffic and very high page rank then it will help..will more help in yahoo search instead of Google search..