background 渐变兼容

background: -webkit-linear-gradient(#EE2825,#F6872B,#f6872b); /* Safari 5.1-6.0 */
background: -o-linear-gradient(#EE2825,#F6872B,#f6872b); /* Opera 11.1-12.0 */
background: -moz-linear-gradient(#EE2825,#F6872B,#f6872b); /* Firefox 3.6-15 */
background: linear-gradient(#EE2825,#F6872B,#f6872b); /* 标准语法 */

background: -webkit-gradient(linear, 0% 0%, 0% 100%, from(#EE2825), to(#F6872B), color-stop(0.5, #f6872b));