<marquee><iframe></iframe></marquee> causes the portion of the layout to shake.

This problems seems not to be limited to <marquee> elements, but all block level elements. I have been using a JavaScript library called window.js (http://prototype-window.xilinus.com/), and from its usage, it seems that <div> elements tear and shake when an <iframe> is moving on top of it. That's why I suspect this applies to all block level elements. (<marquee> is implemented as a block level too, is it? Saw that in html.css.)

(In reply to comment #2) > That's why I suspect this applies to all block level elements. (<marquee> is > implemented as a block level too, is it? Saw that in html.css.) Ugh. I mean, as a block level *element*.

I see this with Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9a2pre) Gecko/20070204 Minefield/3.0a2pre

Hmm, Martijn, a simple marquee { overflow: auto } in html.css seems to fix this. (Adding overflow:auto style to <marquee> is a workaround for this bug, at least for this testcases here)

The "compositor phase 1" patches (https://build.mozilla.org/tryserver-builds/rocallahan@mozilla.com-try-f9bf8fa4178/) seem to have addressed this bug.

Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2a1pre) Gecko/20090722 Minefield/3.6a1pre Works fine now.

Fixed by bug 352093.