My site uses the sidebar-last area to display relevant information on the page. so some pages have blocks in sidebar-last area while some don't. I just noticed that the content-top area compresses when there are blocks present in the sidebar-last. unlike the content-bottom area that stays fixed, the content-top gets smaller.
also is there a way to make the blocks in the sidebar-last area to float a little bit lower so that the blocks appear sort of inline with the content?