var docwidth;
var docheight;
var topoff;

if (self.innerWidth) { 
	// all except Explorer
    docwidth = self.innerWidth;
} else {
    if (document.documentElement && document.documentElement.clientWidth) {
    	// Explorer 6 Strict Mode
    	docwidth = document.documentElement.clientWidth;
    } else {
        if (document.body) {
            // other Explorers
        	docwidth = document.body.clientWidth;
        }
    }
}

if (self.innerHeight) { 
	// all except Explorer
    docheight = self.innerHeight;
} else {
    if (document.documentElement && document.documentElement.clientHeight) {
    	// Explorer 6 Strict Mode
    	docheight = document.documentElement.clientHeight;
    } else {
        if (document.body) {
            // other Explorers
        	docheight = document.body.clientHeight;
        }
    }
}

function popup() {
    if (window.pageYOffset) {
        topoff = window.pageYOffset;
    } else {
        if (document.documentElement && document.documentElement.scrollTop) {
            topoff = document.documentElement.scrollTop;
        } else {
            topoff = document.body.scrollTop;
        }
    }
    document.getElementById("popup").style.width = "620px";
    document.getElementById("popup").style.height = "500px";
    document.getElementById("popup").style.top = (((docheight/2)-345)+topoff)+"px";
    document.getElementById("popup").style.left = ((docwidth/2)+100)+"px";
	document.getElementById("popup").style.visibility = "visible";
	document.getElementById("popup").style.display = "inline";
}

function start_pop() {
    setTimeout("popup()",30000);
}

function close_popup() {
    document.getElementById("popup").style.width = "0px";
    document.getElementById("popup").style.height = "0px";
    document.getElementById("popup").style.top = (((docheight/2)-145)+topoff)+"px";
    document.getElementById("popup").style.left = ((docwidth/2)-145)+"px";
	document.getElementById("popup").style.visibility = "hidden";
	document.getElementById("popup").style.display = "none";
}