//author:div-css

function show(num){ 
 for(var i=1; i<6; i++){ 
 if(i==num){ 
 var a=document.getElementById("nav2a1_"+i); 
 a.style.display="block";        
 }
 else{
 //
 }
 }
}

//这里是关闭函数
function none(num){
 var b=document.getElementById("nav2a1_"+num);
 b.style.display="none";
}