吸顶条或者其他的吧
<!DOCTYPE html>
<html>
<head>
<style>
*{margin: 0;padding: 0;list-style: none;}
body{
width: 1180px;
margin: 0 auto;
}
.head{
width: 100%;
height: 60px;
background: red;
}
.main{
margin: 30px 0 ;
height: 100%;
overflow: hidden;
}
.foot{
width: 100%;
height: 40px;
background: #000;
clear: both;
}
.left{
float: left;
width: 210px;
height: 1300px;
border: 1px solid red;
background: green;
}
.right{
float: right;
width: 930px;
height: 900px;
border: 1px solid red;
background: #ccc;
}
</style>
<!--
<script>
(function(){
window.onresize=window.onscroll=window.onload=function (){
var oDiv=document.getElementById('form-wrap');
var scrollTop=document.documentElement.scrollTop || document.body.scrollTop;
var clientHeight=document.documentElement.clientHeight;
var t=document.body.scrollHeight;
var bodyH= scrollTop+clientHeight;
if(Math.abs(bodyH - t ) < 5){
oDiv.style.bottom='40px';
}else{
oDiv.style.bottom='0px';
}
};
})();
</script>
-->
<script>
window.onload= window.onscroll=function(){
var oLeft = document.getElementById('left');
var oRight = document.getElementById('right');
var scrollTop = document.documentElement.scrollTop || document.body.scrollTop;
//当left的height最大为right的高
if(oLeft.offsetHeight >oRight.offsetHeight){
oLeft.style.height =getStyle(oRight,'height') +'px';
}
//当left的scrollTop为0，fixed
if(scrollTop > oLeft.offsetTop){
oLeft.style.position ='fixed';
oLeft.style.top = '0';
if(oLeft.offsetHeight<oRight.offsetHeight){
oLeft.style.height =getStyle(oRight,'height') +'px';
}else{
oLeft.style.height =document.documentElement.clientHeight -70 +'px';
}
}else{
oLeft.style.position ='';
}
function getStyle(obj,name){
return obj.currentStyle ? obj.currentStyle[name] :getComputedStyle(obj, false)[name];
}
}
</script>
</head>
<body>
<div class="head"></div>
<div class="main">
<div class="left" id="left">
<ul>
<li>菜单1</li>
<li>菜单2</li>
<li>菜单3</li>
<li>菜单4</li>
<li>菜单5</li>
</ul>
</div>
<div class="right" id="right">这里是内容</div>
</div>
<div class="foot"></div>
</body>
</html>