The header is a little mixed up in the issue view, i.e. something doesn't float :) Example bugreport: https://bugzilla.xfce.org/show_bug.cgi?id=10546 Screenshot of what I get with FF: http://i.imgur.com/Dtn0OI4.png
And I think it gets even more weird after I edit a bug: http://imgur.com/IDUZTg0
Fixed with the latest push to the style; navigation now correctly appears outside the main container.