function show_promo()
{
    var promo = document.getElementById('promo');
        promo.style.display = 'block';
        
    var background_div = document.createElement('div');
        
        background_div.className = 'background_div';
        background_div.id = "background_div";
        background_div.innerHTML = "&nbsp";
        background_div.style.width = document.body.offsetWidth + 'px';
        background_div.style.height = document.body.offsetHeight + 'px';
        
        if(navigator.appName == 'Microsoft Internet Explorer')
        {
            var new_height = document.body.offsetHeight + document.body.scrollTop;
            background_div.style.height = new_height + 'px';
        }
        
        document.getElementsByTagName("body")[0].appendChild(background_div);
}

function unshow_promo()
{
   background_div = document.getElementById('background_div');
   document.getElementsByTagName("body")[0].removeChild(background_div);
   
   var promo = document.getElementById('promo');
   promo.style.display = 'none';
}