//随屏滚动
var id=function(o){return document.getElementById(o)}
var scroll=function (o){
	var space=id(o).offsetTop;
	id(o).style.top=space+'px';
	void function(){
		var goTo = 0;
		var roll=setInterval(function(){
			var height =document.documentElement.scrollTop+document.body.scrollTop+space;
			var top = parseInt(id(o).style.top);
			if(height!= top){
				goTo = height-parseInt((height - top)*0.9);
				id(o).style.top=goTo+'px';
			}
			//else{if(roll) clearInterval(roll);}
		},50);
	}()
}

//拖拽功能
  
var dragObject  = null;   
var mouseOffset = null;   
 
//得到鼠标的位置
function mouseCoords(ev){
	if(ev.pageX || ev.pageY){
   		return {x:ev.pageX, y:ev.pageY};
	}
	return {
   		x:ev.clientX + document.body.scrollLeft - document.body.clientLeft,
   		y:ev.clientY + document.body.scrollTop - document.body.clientTop
	};
}
  
function getPosition(e){   
	var left = 0;   
	var top  = 0;   
 
	while (e.offsetParent){   
 		 left += e.offsetLeft;   
 		 top += e.offsetTop;   
 		 e = e.offsetParent;   
	 }   
  
 	left += e.offsetLeft;   
 	top  += e.offsetTop;   
 	return {x:left, y:top};   
}   

function getMouseOffset(target, ev){   
	ev = ev || window.event;     
 	var docPos    = getPosition(target);   
	var mousePos  = mouseCoords(ev);   
	return {x:mousePos.x - docPos.x, y:mousePos.y - docPos.y};   
}    

function mouseMove(ev){   
	ev = ev || window.event;   
	var mousePos = mouseCoords(ev);   
 	if(dragObject){   
 		dragObject.style.position = 'absolute';   
 		dragObject.style.top = mousePos.y - mouseOffset.y;   
  		dragObject.style.left = mousePos.x - mouseOffset.x;   
  		return false;   
 	}   
} 

function mouseUp(){   
	dragObject = null;   
}   
  
function makeDraggable(item){   
	if(!item) return;   
 	item.onmousedown = function(ev){   
  		dragObject  = this;   
  		mouseOffset = getMouseOffset(this, ev);   
  		return false;   
 	}   
	item.onmousemove = mouseMove;
	item.onmouseup = mouseUp;
}