利用css写三角形，兼容IE7

.arrow-up {
            width:0px;         height:0px;         border-left:10px solid transparent;          border-right:10px solid transparent;         border-bottom:10px solid red;          font-size:0px;         line-height:0px;        margin: 0 auto;    }     .arrow-down {
            width:0px;         height:0px;         border-left:10px solid transparent;         border-right:10px solid transparent;         border-top:10px solid blue;         font-size:0px;         line-height:0px;     }             .arrow-left {
            width:0px;         height:0px;         border-bottom:10px solid transparent;         border-top:10px solid transparent;         border-right:10px solid #DC143C;         font-size:0px;         line-height:0px;    }     .arrow-right {
            width:0px;         height:0px;         border-bottom:10px solid transparent;         border-top:10px solid transparent;         border-left:10px solid #FF00FF;         font-size:0px;         line-height:0px;     }

 

效果如下：