This provides an internal property known as hasLayout in Internet Explorer versions 7 and lower.
The definitive article on the subject is here: http://www.satzansatz.de/cssd/onhavinglayout.html
A lot of Internet Explorer’s rendering
inconsistencies can be fixed by giving
an element “layout.” In this article,
the authors focus on some aspects of
this complicated matter.“Layout” is an IE/Win proprietary
concept that determines how elements
draw and bound their content, interact
with and relate to other elements, and
react on and transmit application/user
events.
For an example of a specific bug that zoom: 1 (and so hasLayout) helps to fix:
Inline block doesn’t work in internet explorer 7, 6