The clip CSS property is only supposed to apply to absolutely positioned elements. Change divContainer to have an absolute position and it will work.
Edit: What I said above is actually wrong. The CSS property should work for any element with overflow: set to anything but visible. Which you have done. Oh, the link to the spec is
here.
However, I am sure I seen something about having to use position: absolute somewhere, but maybe that is only supposed to apply to safari...
Anyway, it works if you do set it to absolute, but it'll mean you'll have to change the CSS somewhat. Just go with Phils suggestion if you want an easy life
Edit (again): OK. It seems like Safari has issues with floating the element. (Your float: left). Taking that out and everything seems to work (apart from layout). So there's a bug in Safari's layout engine I never knew of - it can't set dimensions of relatively positioned floating elements...
Oh. Next time, I'll go through a problem thoroughly rather than posting a tonne of edits like this