function activate(num)
   {
		if(!document.getElementById(num)) return;
       if(document.getElementById(num).style.display=='none') state=true;
   else state=false;
   document.getElementById(num).style.display = state?'block':'none';
   if (state) active_layer = num;
   }
function deactivate_all()
   {
   for(var i = 1; i<=100; ++i)
      {
      activate("layer_" + i);
      }
   }
onload=deactivate_all;