js：

    var posX;
    var posY;
    fdiv = document.getElementById("divBody");
    document.getElementById("divHead").onmousedown=function(e)
    {
    if(!e) e = window.event;  //IE
    posX = e.clientX - parseInt(fdiv.style.left);
    posY = e.clientY - parseInt(fdiv.style.top);
    document.onmousemove = mousemove;
    }
       
    document.onmouseup = function()
    {
    document.onmousemove = null;
    }
    
    
    function mousemove(ev)
    {
    if(ev==null) ev = window.event;//IE
    fdiv.style.left = (ev.clientX - posX) + "px";
    fdiv.style.top = (ev.clientY - posY) + "px";
    }

html：

<div class="divBody" id="divBody" style="left: 29px; top: 14px;">  <!--这里要加style="left: 29px; top: 14px;" 否则有问题-->
  <div class="divHead" id="divHead" style="cursor: move;">
  </div>
  <div class="content">
  </div>
  <div class="tail">
   </div>
</div>

css:

.divBody{
//margin-top:20px;
border: solid #CCC 1px;
width:500px;
height:400px;
position:relative;
z-index:0;
    margin-left:auto; 
    margin-right:auto;
}
.divHead{
width:500px;
height:50px;
background-color:#CCC;
}
.content
{
width:500px;
height:300px;
}
.tail{
background:#CCC;
height:50px;
width:500px;
display:table-cell;
vertical-align:middle;
}