.top-corner(@h, @w) {
	height:@h;
	margin-bottom:-@h;
	overflow:hidden;
	width:@w;
}
.complex {
	/* this zoom required for IE5.5 only*/
	*position:relative;
	*zoom:1;
	overflow:hidden;
	.tl, .tr {
		/* position/zoom required for IE7, 6, 5.5 */
		.top-corner(@height0, @width0)
	}
        ....