function changestyle(o,pgup_id,pgdn_id,pra,vid) {
            var nextID = pgdn_id;
            var prevID = pgup_id;
			
            if (window.event.offsetX >= o.clientWidth / 2) {
                o.style.cursor = "url(/Image/right.cur),auto";
				var gourl="?"+vid+"="+nextID+pra;
                if(nextID > 0)
                {
                    o.alt = "点击显示下一张";
                    document.getElementById("alink").href = gourl;				
                   
                }
                else
                {
                    o.alt = "已经到底了";
                    document.getElementById("alink").href = "#";
                }
            }          
		  else
		   {
                o.style.cursor = "url(/Image/left.cur),auto";
				var gourl="?"+vid+"="+prevID+pra;
                if(prevID > 0)
                {
                    o.alt = "点击显示上一张";
                    document.getElementById("alink").href = gourl;
                }
                else
                {
                    o.alt = "已经到头了";
                    document.getElementById("alink").href = "#";
                }
            }
 }