css 背景图片自适应分辨率大小 兼容

拉伸，all浏览器兼容
.bg{
    background:url(http://wyz.67ge.com/wp-content/uploads/qzlogo.jpg);
    filter:"progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod='scale')";
    -moz-background-size:100% 100%;
    background-size:100% 100%;
}