CSS3向下兼容那些事

gistfile1.css

.data-sheet tr:first-of-type th.selected {  /* Others */
	background-image: url(/img/data_sheet_th_selected_bg.png);
	background-repeat: repeat-x;
	height: 31px;
}
.data-sheet tr.first th.selected { /* IE6/IE7/IE8 */
	background-image: url(/img/data_sheet_th_selected_bg.png);
	background-repeat: repeat-x;
	height: 31px;
}

/*
 * 又一段这样的代码，不论浏览器是否支持:first-of-type，都将会执行第二条样式，何必呢？
 */