兼容ie的background-size: cover;

.bg{
    background: url() no-repeat;
    background-size:cover;
    filter: progid:DXImageTransform.Microsoft.AlphaImageLoader( src='../image/bg.jpg', sizingMethod='scale');
    -ms-filter: "progid:DXImageTransform.Microsoft.AlphaImageLoader( src='../image/bg.jpg', sizingMethod='scale')";
}