To emulate max-width (or max-height, min-width or min-height with some modification) for IE, you can use:

width:expression( document.body.clientWidth > 500 ? 500 : "auto" );

Where both 500's are the max-width you want to use. "expression()" is IE-specific and will be ignored by other browsers. This means it's browser proprietary code, which is generally frowned upon, but readability goes before code perfection in my opinion.