var cover = document.getElementById("cover");
cover.style.width = document.documentElement.scrollWidth+"px";
cover.style.height = document.documentElement.scrollHeight+"px";
cover.style.display = "block";
}
#cover{
background:gray;
position:absolute;
left:0px;
top:0px;
display:none;
z-index:20;
filter:alpha(opacity=60);
opacity:0.6 !important;
}
