I definitely think this is a function which should be implemented by the browser, like the Print and Back/Forward buttons. However, except for the Home key, there is currently no such button in the browser, nor any menu item refering to it. So, no one could get to know the shortcut without accidentally finding it out.
Hence, I propose to add a small horizontal line above the scrollbar, which would scroll to the top of the page, and one beneath the lower triangle. This is something which could be generally available everywhere in the operating system, so, for example, you could use these handy little things too in your text editor.

Otherwise, I think it could form an entry in the "Go" menu of Firefox, underneath the Back, Forward and Home entries.

P.S: The title tag of this page currently contains "Top of Page - www.avmdanse.com - www.avmdanse.com". You may want to remove the double www.avmdanse.com

Behold! I give you...

the "Home" key!

Waste of space on shorter pages.

On longer pages, like 2 screens or so, maybe. An script to detect the height of the screen could be used to generate the link at the end of the page if the height reaches some treshold.

Andrew Herron says: Behold! I give you...

the "Home" key!

I think we discussed the fact the 'Home' key is mostly overlooked, sometimes unheard of, not to mention often requireing the use of a function or Alt key on some keyboards.

Home keys don't work!