function prelode() {
	imgs = new Array(6);
   	for (var i=1; i<6; i++){
  		imgs[i] = new Image();
  		imgs[i].src = "http://www.dalian2.cn/templates/default/images/ch_btn_" + (i) + "n.gif";
  	}
	chtype(1);
}

function chtype(num) {
	for(key=1; key<6; key++){
		if(num == key){
		document.getElementById("btn"+key).src = imgs[key].src;
		document.getElementById("name"+key).style.display = "block";
		}
		else{
		document.getElementById("btn"+key).src = "http://www.dalian2.cn/templates/default/images/ch_btn_"+key+".gif";
		document.getElementById("name"+key).style.display = "none";
		}
	
	}
	rol = num;
}

function roll (place,ob,sc) {
	if(rol != place){
  		ob.src = sc;
		}	
}