HTML and CSS Reference
Figure 2.2 An element with hasLayout revealed via the Developer Toolbar in IE7.
Unfortunately, the distinction between an element that goes into the
bucket that gets the extra internal presentation logic and one that
doesn't leads to one of the most commonly attributed problem in
Internet Explorer 6 and 7, called the Peekaboo bug.
The Peekaboo bug is so named because a block of content on a page may
disappear (or flash in and out) while scrolling a page if the block does
not have the hasLayout flag triggered. You can't set the hasLayout flag
directly, but you can “force” it into the proper state by setting one of a
number of CSS properties for the element, including the following:
height: 1% ; /* trigger hasLayout by providing a dimension */
zoom: 1 ; /* trigger hasLayout by using this nonstandard