Issue

IE Mac 5.0:
Element is hidden if it has a position value and is descendant of a floated element.

Floated div.
#floated {
	float: left;
	}
On IE Mac 5.0 you won't see the red div below.
relative div. Won't show up on IE Mac 5.0. But it's there. For example, you can click on a link event if you don't see it. 
#positioned  {
	position: relative;
	}

Tested on: IE Mac 5.0 on System 9.
Doesn't apply to: IE Mac 5.2 on OS X.

Workaround

Add a position value to the floated element.

Floated div with position value.
#floatedPositioned {
	position: relative;
	float: left;
	}
relative div. 
#positioned  {
	position: relative;
	}