// JavaScript Document
function tab(num,num){ 
for(var id=1;id<=4;id++) {
var bg="title"+id;
var text="content"+id;
if(id==num){ //显示、隐藏
document.getElementById(bg).style.display="block";
document.getElementById(text).style.display="block";}
else{
document.getElementById(bg).style.display="none";
document.getElementById(text).style.display="none";} 
}
}