//function $ is conflicted with jquery in whmcs, change to $getE
function $getE(d){
	return document.getElementById(d);
}

function showTab(tab){
   if (typeof curTab == "undefined"){ curTab = "nav-home"; }
   if (curTab != tab.id) {
      $getE(curTab).className = ""; 
      $getE(curTab +"-menu").style.display = "none"; 
   }

   tab.className="on"; 
   curTab = tab.id;	  
   $getE(tab.id +"-menu").style.display = "block"; 
   return false;
}