Safari (only tested 2.0.3) fires :hover outside the borders of an overflowe:d element if it's containing floating element. The :hover will trigger outside the element on Safari. Neither MSIE6 or Firefox has this bug.
Test page Workaround is included
Reported by: Martin Str�m.
Safari | Reported on 5 June 2006.
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1 Posted by David Kilzer on 23 December 2006 | Permalink
Verified fixed as of WebKit r18399.
http://bugs.webkit.org/show_bug.cgi?id=9610#c3