针对不同浏览器，背景渐变的兼容问问题！
background: -ms-linear-gradient(top, #fff, #0000ff); /* IE 10 */
background:-moz-linear-gradient(top,#b8c4cb,#f6f6f8);/*火狐*/
background:-webkit-gradient(linear, 0% 0%, 0% 100%,from(#b8c4cb), to(#f6f6f8));/*谷歌*/
background: -webkit-gradient(linear, 0% 0%, 0% 100%, from(#fff), to(#0000ff)); /* Safari 4-5, Chrome 1-9*/
background: -webkit-linear-gradient(top, #fff, #0000ff); /*Safari5.1 Chrome 10+*/
background: -o-linear-gradient(top, #fff, #0000ff); /*Opera 11.10+*/
