15746 2012-01-27 18:13:21 +0000 Margin collapsing: zero-height, zero-min-height boxes with self-collapsing children no longer themselves self-collapse 2012-12-04 00:54:25 +0000 1 1 1 Unclassified CSS CSS Level 2 unspecified All Windows 3.1 NEW P2 normal --- 1 antonsforums bert public-css-bugzilla oldest_to_newest 63193 0 antonsforums 2012-01-27 18:13:21 +0000 Reported by Anton Prowse Consider the following test case: <div style="margin:10px 0; height:0"> <div style="margin:10px 0"></div> </div> The parent's margins don't collapse according to the current normative rules concerning adjacency since the bottom margin of the child is not adjacent to the bottom margin of the parent. (Specifically, in this situation, the child self-collapses and the resulting margin collapses with the parent's top margin, but this new resulting margin doesn't collapse with the parent's bottom margin.) But this makes the following note found in 8.3.1 incorrect: # A box's own margins collapse if the 'min-height' property is zero, and # it has neither top or bottom borders nor top or bottom padding, and it # has a 'height' of either 0 or 'auto', and it does not contain a line box, # and all of its in-flow children's margins (if any) collapse. When a box's height is 0 then the note holds only when the box has no children, whereas when its height is 'auto' the note holds as given. If this change is desirable, then to resolve the conflict we could replace the item in the note with: | * A box's own margins collapse if the 'min-height' property is | zero, and it has neither top or bottom borders nor top or | bottom padding, and it does not contain a line box, and it | either has a 'height' of 0 and no in-flow children or it has | a height of 'auto' and all of its in-flow children's margins | (if any) collapse. See: http://lists.w3.org/Archives/Public/www-style/2010Sep/0698.html See also Bug 15745 which describes another conflict with the note mentioned.