See attachment. Seen on Windows 8 + IE 10.
Tried to quickly fix it myself but couldn't.
I'm not able to reproduce it on a Win8 / IE10 test vm. It even does not occur when having IE 10 in combat mode or in IE9 document mode... Any steps how to reproduce?
I only open Piwik demo and that's it. I probably use an outdated version of IE10 (see about in screenshot) as I'm missing some updates on that VM. It looks good on Saucelabs with IE10+Win8 as well.