open the url 'www.arstechnica.com' and scroll to the right you will see that the background does not display correctly in the rightmost area of the page (where it says 'Reviews:', 'Articles', etc.)
The issue is a problem with CSS compatability with the rest of the world in handling blocks whose children are larger than the block.
Actually, there is a more serious problem here. Shrink the viewport so that the right hand sidebar is not visible. Move the horizontal scroll bar all the way to the right so that the left hand side scroll bar is no longer visible. Now widen and reshrink the window. There are some very dodgy things going on here, particularly with undefined backgrounds. There is a copy of this page here: http://www.bath.ac.uk/%7Epy8ieh/internet/projects/mozilla/arstechnica.html I intend to boil that page down to a minimal test case.
I have replaced the copy of the original page which is given above with a minimal test case showing the problem: http://www.bath.ac.uk/%7Epy8ieh/internet/projects/mozilla/arstechnica.html The problem is that blocks that are wider than the viewport do not redraw correctly when the viewport is resized. The above test page is self explanatory, and gives the steps required to reproduce the bug.
The above (www.bath.ac.uk) testcase works for me under M7/Linux. The www.arstechnica.com site still exhibits the non-displaying background if you scroll to the right, though.
To see the problem on the small (www.bath.ac.uk) test case, you have to first open the page, then scroll right, *and then resize your window*. I'll look into making the small test case better.
I've improved the test case. The (same) bug is now much more clearly visible. email@example.com: Thanks for prompting me.
This problem doesn't occurs on M8 release. Already fixed?
I can't reproduce the problem anymore, so I'm closing the bug. Please reopen or make a new more specific bug if there actually is something there. The testcase and the original url render flawlessly now :-)
I'm not seeing this problem either with the Sept 23rd build.