IE used to have dynamic CSS properties [0], which were most often used in the wild to achieve max-width in IE [1] (at huge cost — in the linked article the auth

IE used to have dynamic CSS properties [0], which were most often used in the wild to achieve max-width in IE [1] (at huge cost — in the linked article the author warns against using the very performance-expensive technique). But the way that technique is implemented is actually very similar to what you're describing: the CSS causes the selected element to examine some of its DOM properties and conditionally apply styles on a per-property basis. Maybe this is another great old IE quirk that needs some W3 loving? [0] http://msdn.microsoft.com/en-us/library/ms537634(v=vs.85).aspx http://msdn.microsoft.com/en-us/library/ms537634(v=vs.85).as... [1] http://www.svendtofte.com/stylesheets/reflections-on-max-width/ http://www.svendtofte.com/stylesheets/reflections-on-max-wid...