Question on collapsing margins and block reflow context roots

• From: Boris Zbarsky <bzbarsky@MIT.EDU>
• Date: Wed, 26 Jan 2005 23:50:12 -0600
• To: www-style@w3.org
• Message-ID: <41F88114.5030604@mit.edu>

Section 8.3.1 [1] explicitly lists a number of types of boxes for which margins 
do not collapse.  This list happens to coincide with the list of block reflow 
context roots (with the exception of "'overflow' other than 'visible'" elements, 
for which the implication is that their margins collapse with their siblings).

So my questions are:

1)  Do the margins of boxes with non-visible overflow set collapse with their
     siblings?
2)  If not, would it not make more sense to just say that all block reflow
     context margins do not collapse?

The reason I ask is that there may be some "replaced elements" (I put that in 
quotes because they aren't quite) that effectively act like block reflow context 
roots in some UAs (HTML's <button> and <fieldset> come to mind), and it would be 
good to have a guideline as to how margin collapsing should work for those elements.

-Boris

Received on Thursday, 27 January 2005 07:01:30 UTC