This probably isn't the most effective summary, but I haven't done any investigative work to determine the cause. Here are the steps to reproduce, though. Visit the URL: http://johneepixels7.tumblr.com/post/1343104367 Ignore the videos/images on the left and notice that the actual page content is down below the left column (ends at the search box), and that it is mostly hidden off to the left of the viewport (without the ability to scroll). This was present in 4.0b6 and is still present in the latest or so Minefield (build ID: 20101015031104). tn says it's a regression from 3.6. It works fine in Safari 5.0.2 (where you can see roughly what it's *supposed* to look like).

Regression range: http://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=83c887dff0da&tochange=d6bb0f9e9519

And flipping the html5 pref fixes the bug.

Hmm... it appears that it may be caused by a runaway <object> that is not automatically closed within a <div />: <div style="width:200px; "><object width="200"><img src="http://dailybooth.com/johneepixels7/latest/medium.jpg"></div>

Blocking to at least figure out whether this is a bug in our parser or in the spec. Henri, can you have a look?

(In reply to comment #4) > Blocking to at least figure out whether this is a bug in our parser or in the > spec. Henri, can you have a look? This is a feature of the spec. This has been seen before as bug 588357. The corresponding spec bug was WONTFIXed. If we care about pushing this on the spec front, the most useful next step would be reading the source of WebKit's old tree builder to figure out what exactly it used to do.

I reopened the spec bug: http://www.w3.org/Bugs/Public/show_bug.cgi?id=10427

Resolving WONTFIX, because Hixie WONTFIXed the spec bug again pointing out that http://johneepixels7.tumblr.com/post/1343104367 renders the same in Firefox trunk, Chrome trunk, IE8 and the latest Opera. Yay interop.