經(jīng)驗(yàn)值：
<span class="progress-bar"><b style="width:50px;"> </b></span>

.progress-bar, .progress-bar b{background: url("/images/ico.png") no-repeat scroll 0 0; display: block;}
.progress-bar {background-position: 0 0; height: 15px;width: 430px;}
.progress-bar b {background-position: 0 -17px; height: 12px;}