When 'overflow' is set, the element is focusable. There is nothing in CSS 2.1 which says that this is correct. This was caused by bug 72747. <http://www.w3.org/TR/2004/CR-CSS21-20040225/visufx.html#overflow>
Isn't this required for accessibility reasons?
Probably the same as bug 257938.
It is. That bug describes how I discovered "the bug". *** This bug has been marked as a duplicate of 257938 ***