css 小技巧总结一

	.img-box{
		position: relative;
		width: 20%;
		height: 0;
		padding-bottom: 15%;
		overflow: hidden;
	}
	.img-box img{
		position: absolute;
		top: 0;
		right: 0;
		bottom: 0;
		left: 0;
	}

.demo {
      width: 0;
      height: 0;
      border-left: 50px solid transparent;
      border-right: 50px solid transparent;
      border-bottom: 50px solid red;
      border-top: 50px transparent solid;
    }