Scrollable part above fixed part in html container

As a follow-up of the previous post, I also want to publish a solution for the next situation: what if there is no fixed part above the scrollable part? Problem here is that setting top undoes setting the bottom in IE.
So we have to make sure that the top is not set in IE6 (using ones of the infamous CSS hacks):

html>body .content{
/* this part is moved out of the common part,
and will only be taken into account if the browser is not IE6 */
top: 0;
}


Now we still have to make that the height is correct in IE6, as the height is set to auto by default:

height: expression((offsetHeight +offsetTop)+'px');

The problem is that we can't retrieve the bottom from javascript,
so we have to rely on the fact that the height is set automatically, and the top will be set accordingly. We want the following: newHeight = parentHeight - bottomOffset, while bottomOffset = parentHeight -topOffset.