Note: April 7th, 09'. Adds ability to scroll to an absolute position (from top of page) or specific element on the page instead. Also fixes scroll animation not working in Opera.
Description: If your pages are long winded, it's a good idea to provide viewers with an easy way to quickly/ automatically scroll back to the top of the page. That's where this script comes in. It displays a stationary control at the lower right corner of the window that when clicked on gently scrolls the page back up to the top. And instead of always being visible on the user's screen, the script lets you specify how far down the page the user is at (in pixels) before revealing the control. Nifty!
Note that apart from displaying a stationary control, you can also define arbitrary anchor links on the page with a special href value (ie: #top) that when clicked activate the script and scrolls the page back to the top.
Demo: Scroll the page down (at least 100 pixels) to see a "Back to Top" control appear at the lower right of the window.