Scroll Control

This may seem unneeded at first, but I've actually found a purpose for 
it while doing a complex design involving fixed positioning.  It would 
be nice to have some way of specifying the document's scrolling region. 
  This is a minimal example which I would apply to my particular case, 
so feel free to elaborate on it:

body {
	bottom-scroll: 200px;
}

That may not be the best way to do it, this is just from the top of my 
head.  In my case, I've used fixed positioning to place a sort of 
footer on the bottom of the page that stays there when the page is 
scrolled.  It fits nicely with the rest of the design and such.  The 
problem is that it covers up the main content region, which I've used 
z-index to place "under" the footer.  When you scroll to the bottom of 
the page, there's a good portion of the content region which is 
obscured.  If I could just scroll a little more, I'd be able to see the 
rest, but as far as the browser is concerned, I've already reached the 
bottom of the page.  A temporary solution is to add a 200px margin to 
the bottom of the content box, but that's pretty unreliable, as not all 
browsers regard it necessary to scroll the margin up.  Using padding, 
which I've resorted to for now, sort of takes away from what I'm trying 
to get at, and I don't think it should be necessary to resort to 
altering the look of the page.  Another problem is that I don't 
necessarily know the height of the user's screen, so other "hacky" 
techniques would be incomplete and, well, sloppy.  This varying screen 
heights also means that the padding solution may even be inadequate.

It seems kind of like a specific request, so I'm not sure if it would 
really be useful to anyone else, but it could be.

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