css 渐变兼容写法 ie chrome firefox
background: -webkit-gradient(linear, 0% 0%, 0% 100%, from(#33bbee), to(#00a0e9));
background: -moz-linear-gradient(top, #33bbee, #00a0e9);
background: -o-linear-gradient(top,#33bbee, #00a0e9);
background: -ms-linear-gradient(top,#33bbee 0%,#00a0e9 100%); /IE10+/
-ms-filter: progid:DXImageTransform.Microsoft.gradient(gradientType=0,startColorstr=#33bbee, endColorstr=#00a0e9); /IE/
filter: progid:DXImageTransform.Microsoft.Gradient(gradientType=0,startColorStr=#33bbee,endColorStr=#00a0e9);/IE6,7/