A fluid wrapper (gray) contains:
In IE7-/Win if the browser window is narrowed, there is a point when the green box drops vertically below the float. This is not correct.
The wide orange box is an attempt to prop the wrapper sufficiently wide to avoid the fall of the green box. But it is not sufficient: in IE6- the wrapper expands to include it, but the fall still occurs (and the blue bordered box still continues to shrink, showing that there is NOT a sort of min-width emulation.)