问题10：获取当前页面宽度JS

  var mleft=document.getElementById("mleft");
  var h = document.documentElement.clientHeight;
  mleft.style.height=h-68+"px";

水平滚动条：<div style="100px;overflow-x:auto"></div>

垂直滚动条：<div style="height:300px;overflow-y:auto"></div>

水平加垂直：<div style="100px;height:300px;overflow-x:auto;overflow-y:auto"></div>