利用css来画出各种样式不同的梯形

<div class="mask"></div>

.mask
{
    height: 0;
    width: 100px;
    border-top: 100px solid red;
    border-right: 37px solid transparent;
}

.mask
        {
            width:100px;
            height:0;
            border-width:0 37px 100px 37px;
            border-style:none solid solid;
            border-color:transparent transparent red;
        }

.mask
        {
            width:100px;
            height:0;
            border-top: 100px solid red;
            border-right: 37px solid transparent;
            border-left:37px solid transparent;
        }

 .mask
        {
            width:100px;
            height:0;
            border-top:100px solid red;
            border-left:37px solid transparent;
        }

.mask
        {
            width:100px;
            height:0;
            border-bottom:100px solid red;
            border-left:37px solid transparent;
            margin-left: -30px;
        }