CSS3让图片作为整页背景且适应各种比例

示例代码如下

<!DOCTYPE html>
<html lang="zh-CN">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <style>
    #web_bg {
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      height: 100%;
      background-image: url(/bg.jpg);
      z-index: -10;
      zoom: 1;
      background-color: #fff;
      background-repeat: no-repeat;
      background-size: cover;
      -webkit-background-size: cover;
      -o-background-size: cover;
      background-position: center 0;
    }
  </style>
</head>

<body>
  <div>
    <!--背景图片-->
    <div id="web_bg"></div>
    <!--其他代码 ... -->
  </div>
</body>

</html>