Test passes if there is a 300px tall filled green square and no red.

Firefox 3.6, Opera 10.10, Safari 4.0.4 and Seamonkey 2.x pass this test.

Credit must go to Matt Bradley from InventPartners for originally reporting this bug in Internet Explorer 8: Top margin missing from first element after floated elements and clearing <div>

Valid HTML 4.01! CSS compliant