The problem showed up on some pages on Lynda.com. IE 11 does not have the problem. Here is a screen shot of a problem page on Lynda.com in FF, showing the column displaying wrongly: https://support.cdn.mozilla.net/media/uploads/images/2015-04-08-23-33-54-0d7e35.png And here is a screen shot of the same page in IE 11, displaying properly: https://support.cdn.mozilla.net/media/uploads/images/2015-04-08-23-35-00-77f7ad.png Troubleshooting steps so far: 1. Refresh FF. No joy. 2. Disable all add-ons. No joy. 3. Run FF in safe mode. No joy.