Then both syntax are merged. I use the Pixy's underscore hack, but with sign #. A CSS property written with the underscore on the start is visible for Internet Explorer (all versions but IE 7), property with # on the start is visible for all IE version (IE7 included). But such written property is invisible for any other standard browser (e.g. Explorer interprets _position: absolute; unlike other browsers). Underscore hack seems to be valid, but if you don't want to use it, you may use the more structured code below (not for IE 7).