<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title></title>
  <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
  <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/bootswatch/3.3.7/cerulean/bootstrap.min.css">
  <style type="text/css">
    #header{
      position: fixed;
      top:0;
      left: 0;
      width: 100%;
      height: 80px;
      background: #000;
      z-index: 10;
      background: rgba(0,0,0,.8);
      padding-right: 10%;
      padding-left: 10%;
    }
    #header button{
      color: #fff;
      opacity: 1;  
      line-height: 80px;
    }

    body{
      margin: 0;
      padding: 0
    }
    button{
      outline: none
    }
    .fanhui{
      color: #fff;
      font-size: 18px;
      display: inline-block;
      line-height: 80px;
    }
    .dakai{
      position: fixed;
      right: 10%;
      top: 30px;
      display: none;
    }
  </style>
</head>
<body>
  <div id="header">
    <a href="" class="fanhui">返回</a>
    <button type="button" class="close" data-dismiss="modal" aria-hidden="true">×</button>
  </div>
  <button class="dakai btn btn-primary glyphicon glyphicon-th-list"></button>
  <iframe src="http://demo.gensee.com/webcast/site/entry/join-39880c94a99b4856bfa82008efa8a9aa?nickName=tset" id="myiframe" scrolling="no" οnlοad="changeFrameHeight()" frameborder="0" width="100%"></iframe>
</body>
<script type="text/javascript">
    var clientHeight=document.documentElement.clientHeight||document.body.clientHeight;
    function changeFrameHeight(){
      var ifm= document.getElementById("myiframe"); 
        ifm.height=clientHeight+'px';
    }
    window.οnresize=function(){  
         changeFrameHeight();  
    }
    $("#header button").click(function(){
      $(this).parent().slideUp();
      $(".dakai").css("display","block");
    });
    $(".dakai").click(function(){
      $("#header").slideDown();
      $(".dakai").css("display","none");
    })
</script>
</html>