In all the following tests the red box has position:relative. To check its rendering it is sandwiched between two boxes (grey, zero margins, static position.)
With a slightly bigger than normal line height. In IE7-/Win the relative box is not fully rendered in the top part: there is a white stripe between the first two boxes.
With a bigger line height. The problem is more evident.
With hasLayout on the relative box, the problem disappears.
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