Replying to Back and forward through pages.

Ok. I might have a little trouble getting my point across, so bear with me if you will.

On some sites, I've noticed that if you are on a certain page at point "x" somewhere scrolled down the page, and then you hit back on the browser, then immediately hit forward, the site will automatically scroll down to point "x" for you rather than starting at point "a" at the top.

Hopefully that makes sense. But I was wondering why NS doesn't do that. Is it a cookie issue? It would be super convenient because sometimes threads get long and sometimes I have to hit back, and when I click forward again, I'm at the top of the thread/page instead of where I was before.

Does anyone get what I'm trying to say? It's more curiosity than anything.