With IE8 coming along to carry on muddying the waters of browsers and compatibility I thought it prudent to note here the method of getting IE8 to emulate IE7 using a meta tag. There are a few reasons for this that I won't go into here but one of the main ones is for old sites not undergoing a code overhaul.

<meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7" />

Should get IE8 to behave in the same way IE7 did and things should look as you made them do when initially designing for Microsoft's inherently flawed browsers.