currentdiv = 'div1'

function dtoggle(newdiv)
{ document.getElementById(currentdiv).style.display = "none";  
  document.getElementById(newdiv).style.display = "block";
  document.getElementById(currentdiv + "_b").className = "classoff"
  document.getElementById(newdiv + "_b").className = "classon"
  currentdiv = newdiv; }