function show(par) {
   var div_par = document.getElementById(par);
   if (div_par.style.display == 'none'||div_par.style.display == '')
     div_par.style.display = 'block';
   else
     div_par.style.display = 'none';
 }

function showall() {
     document.getElementById('tab1').style.display = 'block';     
     document.getElementById('tab2').style.display = 'block';     
     document.getElementById('tab3').style.display = 'block';     
}