function toggle_callback(div) 
{
var option=['callback'];

for(var i=0; i<option.length; i++) 
{ obj=document.getElementById(option[i]);
obj.style.display=(option[i]==div) && !(obj.style.display=="block")? "block" : "none"; }
}

function preloader() 
{
heavyImage = new Image(); 
heavyImage.src = "images/menu_middle.jpg";
}