js实现div在页面拖动效果

<style type="text/css">body { margin: 0px;}#div1 { display: none; position: absolute; z-index: 1000; height: 100%; width: 100%; background: #000000; filter:Alpha(opacity=30);}#div2 { display: none; position: absolute; height: 100%; width: 100%; padding-top: 10%; z-index: 1001;}#div3 { display: block; position: absolute; z-index: 999;}</style><script type="text/javascript">//定义移动对象和移动坐标var Mouse_Obj="none",_x,_y;//拖动对象函数(自动)document.onmousemove=function(){ if(Mouse_Obj!=="none") { document.getElementById(Mouse_Obj).style.left=_x+event.x; document.getElementById(Mouse_Obj).style.top=_y+event.y; event.returnValue=false; }}//停止拖动函数(自动)document.onmouseup=function(){ Mouse_Obj="none";}//确定被拖动对象函数 o为被拖动对象function m(o){ Mouse_Obj=o; _x=parseInt(document.getElementById(Mouse_Obj).style.left)-event.x; _y=parseInt(document.getElementById(Mouse_Obj).style.top)-event.y;}</script><div id="div1"></div><div id="div2" onmousedown="m(this.id)" style="left: 0px;top: 0px;"><table width="50%" border="0" cellpadding="3" cellspacing="1" style="background: #ff7300;position:static;filter:progid:DXImageTransform.Microsoft.DropShadow(color=#666666,offX=4,offY=4,positives=true)" align="left"> <tr style="cursor: move;">  <td><font color="#FFFFFF">温馨提示：</font></td>  <td align="right"><input type="button" value="ｘ"onClick="document.getElementById('div1').style.display='none';document.getElementById('div2').style.display='none';" style="cursor: hand;"></td> </tr> <tr>  <td colspan="2" width="100%" bgcolor="#FFFFFF" height="150"align="middle">欢迎访问　<a href="//www.VeVB.COm">//www.VeVB.COm</a></td> </tr></table></div><div id="div3"><input type="button" value="打开层"onClick="document.getElementById('div1').style.display='block';document.getElementById('div2').style.display='block';"></div>