function show3(n)    
{       
     var o = document.getElementById('title3').getElementsByTagName("a");    
     var c = document.getElementById('content3').getElementsByTagName("div");    
     for(i = 0; l = o.length, i < l; o[i].className = '',c[i].style.display = 'none',i++ );    
     o[n].className = 'over';    
     c[n].style.display = 'block';       
}