When a child of a multi-column element has a top margin, that margin pushes the child down even if the child is at the very top of the column. I don’t know if this is a bug, but Mozilla’s handling of this situation is preferable: it simply gets rid of the margin and makes the text in all of the columns line up at the top.
Created attachment 34917 [details] Test case that shows the bug This test case shows the “bug.” In nightly WebKits, the second paragraph doesn’t line up at the top with the first paragraph. Mozilla’s handling is preferable because I don’t really care about the top margin of the second paragraph; having it line up with the first paragraph is what I really want.
This is not about what you care. This is about the specification, which clearly states: "A top margin set on the first child element of a multicol element will not collapse with the margins of the multicol element." http://www.w3.org/TR/css3-multicol/#the-multi-column-model What is absolutely sensible. Because how would you achieve that effect otherwise? You'd have to introduce another element. And why would you set a top margin if you don't want it in the first place? This is clearly a bug. And in Mozilla, too: https://bugzilla.mozilla.org/show_bug.cgi?id=388666 https://bugzilla.mozilla.org/show_bug.cgi?id=616722 The current Opera snapshots handle this right.
Our behavior is correct according to the spec.