盒子左上角三角形 css

 

<div class="pcode"><span class="picon"></span><span class="pimg">5.5折</span></div>

.pcode {
    position:relative;
    width: 100%;
    background-color: #ccc;
    height: 70px;
}
.picon {
     display: inline-block;
     width: 0;
     height: 0;
     border-top: 37px solid #f00;
     border-right: 37px solid transparent;
     position: absolute;
     top: 0;
     left: 0;
 }
 .pimg {
     color: #fff;
     text-align: center;
     text-shadow: rgba(255, 255, 255, 0.5) 0px 1px 0px;
     -webkit-transform: rotate(-45deg);
     transform: rotate(-45deg);
     -ms-transform: rotate(-45deg);
     -o-transform: rotate(-45deg);
     position: absolute;
     padding: 10px 0;
     left: 0px;
     top: -9px;
     font-size: 12px;
 }