You are no longer painting all of BODY's margin with HTML's background color. You seem to be only painting a rectangle the size of BODY, thus ignoring the right and bottom margins. However, this improves if I switch to another window (Alt+Tab) and then back again Note: this was part of bug #1580, but I made it into a separate bug

Changed test case to equivalent part of W3C CSS Test Suite (bug easier to see).

The bug has now disappeared. However, BODY's margin-top appears to be ignored. This can be seen nicely in http://style.verso.com/boxacidtest/vd/ (This is also noted in bug 1580.)

As far as the BODY's top margin being ignored, this comment in nsBlockFrame is probably related: nsBlockReflowState state(aPresContext, aReflowState, aMetrics, lineLayout); if (NS_BODY_THE_BODY & mFlags) { // Because we use padding to provide some empty space around the // outside of the html body, we need to disable margin application // at the top and bottom. // XXX revisit this when the HTML element is no longer the root of // the frame tree state.mIsMarginRoot = PR_FALSE; } Kipp, now the NS_BODY_THE_BODY flag is getting set on the area frame we create for the HTML element. It's being set so we damage the window when incremental reflow occurs. The same stuff we always had, just now on the HTML element's frame instead of the BODY's frame

For that matter... you're also losing the margin-bottom on BODY when there is a scrollbar.

*** Bug 2053 has been marked as a duplicate of this bug. ***

I've updated the block code to better handle the restructuring recently done to make HTML just another block. This fixes the issue of the top/bottom margins on BODY disappearing.

Chirs can you please verify using the referenced URL

Verifying this as fixed.