Ok, if I understood what you wanted, the problem is that the #Content
div is too high, since you added another div on top.
So you could change the line you indicated in this way:
$("#Content").height($(window).height() - $("#Top-navigation").outerHeight(true)).width($(window).width()-$("#Left-navigation").width());
and I think you should also remove the height
and width
of the Content
div from the HTML.