When you request link trades its important to decide the url you want people to link to you by and stick to it. There's been examples where the PR is no different for a domain with and without the
www. There's also examples that disprove this. I have found that if you have a high PR (5+) then Google is able to make the association that it's all the same site but this isn't always true.
Same goes for the html page or just the directory. Pick a url to use and don't change it or your efforts will be in vain.
WG