Might be a Safari bug only. Try http://www.extractwidget.com/bug3.html. You will notice some strange stuff on the iframes, and scrollbars did disappear Remove : <style> body { -webkit-perspective: 800; } </style> Everything comes back to normal
Known issue with iframes in compositing layers, somewhat related to bug 15676.
The test site no longer exists. We can't take further action under this bug, but work continues under the related bug.