I have built a site using a child theme of twenty eleven. I have never made any changes to the twenty eleven theme. Up until yesterday, the site looked find across the current versions of all major browsers(Internet Explorer, Firefox, Chrome, Safari, and Opera). Yesterday, I updated to the most current version of twenty eleven and now my header image doesn't display properly in firefox. I cannot provide a link to the site because it is a secure site for the internal processes of an EMS service. However, the two links below show what the site used to look like (and still does in most browsers) and what it looks like post-update in firefox.
The CSS of the child theme does not address the header image at all, so I am at a loss as to why this has happened. When I revert to the original twenty eleven theme, it all displays perfectly (although it doesn't look nearly as nice).
How the site is supposed to look:
How the site now looks in firefox: