If you just use a hash in the href of a back-to-top link, or a hash plus ID, are there any problems with that? Any browsers/other software in which it fails?
It works in the mainstream modern browsers that I've tried, plus IE6, but I can't test any others. Just using a hash on its own seems too good to be true, like it's relying on a bug. Should it go to an anchor, like in WebAIM's article about skip links?