//鼠标事件移动一个对象
//被移动对象div需要加属性id="div" style="position:absolute;top:0;left:0"
//在触发对象p上onMouseMove="drag(this,div)"
function drag(p,o){   
  p.onmousedown=function(a){   
  var d=document;if(!a)a=window.event;   
  var x=a.layerX?a.layerX:a.offsetX,y=a.layerY?a.layerY:a.offsetY;   
  if(o.setCapture)   
  o.setCapture();   
  else if(window.captureEvents)   
  window.captureEvents(Event.MOUSEMOVE|Event.MOUSEUP);   
    
  d.onmousemove=function(a){   
  if(!a)a=window.event;   
  if(!a.pageX)a.pageX=a.clientX;   
  if(!a.pageY)a.pageY=a.clientY;   
  var tx=a.pageX-x,ty=a.pageY-y;   
  o.style.left=document.body.scrollLeft+tx;   
  o.style.top=document.body.scrollTop+ty;   
  };   
    
  d.onmouseup=function(){   
  if(o.releaseCapture)   
  o.releaseCapture();   
  else if(window.captureEvents)   
  window.captureEvents(Event.MOUSEMOVE|Event.MOUSEUP);   
  d.onmousemove=null;   
  d.onmouseup=null;   
  };   
  };   
}