具体代码：
background: -webkit-linear-gradient(top, rgba(255,255,255,0.4)0%, rgba(255,255,255,0.2)75%, rgba(255,255,255,0)98%);/* Safari、Chrome */ background: -o-linear-gradient(bottom, rgba(255,255,255,0.4)0%, rgba(255,255,255,0.2)75%, rgba(255,255,255,0)98%);/* Opera */ background: -moz-linear-gradient(bottom, rgba(255,255,255,0.4)0%, rgba(255,255,255,0.2)75%, rgba(255,255,255,0)98%);/* Firefox */ background: linear-gradient(to bottom, rgba(255,255,255,0.4)0%, rgba(255,255,255,0.2)75%, rgba(255,255,255,0)98%); /* 标准的语法（必须放在最后） */
注意：Internet Explorer 9 及之前的版本不支持渐变。
