JavaScript实现点击按钮或文字显示遮罩层

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>点击文字弹出一个DIV层窗口代码</title>
    <meta charset="urf-8"/>
    <style>
    .black_overlay{
      display: none;
      position: absolute;
      top: 0%;
      left: 0%;
      width: 100%;
      height: 100%;
      background-color: black;
      z-index:1001;
      -moz-opacity: 0.8;
      opacity:.80;
      filter: alpha(opacity=88);
    }
    .white_content {
      display: none;
      position: absolute;
      top: 25%;
      left: 25%;
      width: 55%;
      height: 55%;
      padding: 20px;
      border: 10px solid orange;
      background-color: white;
      z-index:1002;
      overflow: auto;
    }
  </style>
  </head>
  <body>
    <p>示例弹出层：<a href = "javascript:void(0)" onclick = "document.getElementById('light').style.display='block';document.getElementById('fade').style.display='block'">请点这里</a></p>
    <div id="light" class="white_content">这是一个层窗口示例程序. <a href = "javascript:void(0)" onclick = "document.getElementById('light').style.display='none';document.getElementById('fade').style.display='none'">点这里关闭本窗口</a></div>
    <div id="fade" class="black_overlay"></div>
  </body>
</html>