Is there a function that I can call from my skin's _main.php that will link to the top of the page regardless of what page the user is currently on?

In xhtml terms, I want this:

<a href="#">Back to Page Top</a>

... but of course this links to a forbidden or nonexistent file if I use this code in _main.php.

Ideally, this would not even have to load the page anew, and could just work as the '#' option does in a regular xhtml page.

Thanks for your time.