Admin Forum:Monobook tabs seriously dislocated after 1.19 upgrade

Since the 1.19 upgrade, Monobook display has been seriously compromised. Take a look at this screenshot: You'll note that the background for the article proper has been shifted upward such tht it extends all the way to the control panel. The tabs stay where they were before, but are still z-indexed above the article text, which means that most leads are wholly obscured.

So is this a bug, or is it something we now have to find a workaround for? (For what it's worth, this behaviour exists in the latest versions of Safari, Opera, Firefox and Chrome)  07:45: Wed 15 Aug 2012