I think the reason a div will not enclose a floated element is that, because the flow is just working its way some where, and so Div won't enclosed the "clear: both" point if there isn't any... (see post) http://forums.digitalpoint.com/showthread.php?t=370584 I think most of the time, we want the div to enclose the "flow's clearing point"... most of the time, that is... with rare design use that we actually want to not enclose it... (for overlapping effect)... so how about in the CSS 4.0 definition, any div will automatically enclose floated elements, unless there is a declaraction in <div sytle="enclose: none ... " and the default value is "auto", which means it will enclose a floated element.