Div with child elements that are floated.
Note: The height of the parent div (outlined in red) collapses because no child element exists in the flow of the page (because all children are floated) to give it height. This will cause layout problems in the page for adjacent content.

Div with child elements that are floated. The parent container has two CSS properties to define overflow behavior and an IE6 height hack.
Note: The height of the parent div (outlined in red) no longer collapses because overflow:auto forces the height of child elements to be considered.

Code:

parent {  
	overflow:auto;
	_height:1%; /* ie6 fix */
}