Step to reproduce: hover the mouse cursor over the following blue rectangle "I ♥ validator" image
Expected result: a 4px red bordered outline should surround the blue rectangle "I ♥ validator" image
Actual result in IE 8 pre-RC1 Partner build 6001.18344: a 4px red bordered outline does not surround the blue rectangle "I ♥ validator" image
Firefox 1.x, Firefox 2.x, Firefox 3.0.5, Opera 9.63, Safari 3.2, Konqueror 4.1.2, Seamonkey 1.x, Seamonkey 2.x, NS 7.2, K-meleon 1.x all pass this test.
This bug has been reported at connect's IE beta feedback as bug 389799.
Update: this bug has been FIXED in Internet Explorer 8 RC1 (build 6001.18372) released on January 26th 2009. Otherwise, Internet Explorer 8 RC1 PASSES this specific and particular testcase.