function toggle(div_id) {
	var el = document.getElementById(div_id);
	if ( el.style.display == 'none' ) {	el.style.display = 'block';}
	else {el.style.display = 'none';}
}

function blanket_size(popUpDivVar) {
    if (typeof window.innerWidth!='undefined') {
        viewportheight=window.innerHeight;
    }
    else {
        viewportheight=document.documentElement.clientHeight;
    }
    if(document.body.scrollTop>0){
    // For IE 5.5
        bdy_ref=document.body;
    }
    else {
        bdy_ref=document.body.parentNode;
    }
    if ((viewportheight>bdy_ref.scrollHeight) && (viewportheight>bdy_ref.clientHeight)) {
        blanket_height=viewportheight;
    }
    else {
        if (bdy_ref.clientHeight>bdy_ref.scrollHeight) {
            blanket_height=bdy_ref.clientHeight;
        }
        else {
            blanket_height=bdy_ref.scrollHeight;
        }
    }
    var blanket=document.getElementById('blanket');
    blanket.style.height=blanket_height+'px';
    var popUpDiv=document.getElementById(popUpDivVar);
    popUpDiv_height=screen.availHeight/2-180; //210 is the half of the popup’s height
    popUpDiv.style.top=(popUpDiv_height+bdy_ref.scrollTop)+'px';
}

function window_pos(popUpDivVar) {
	if (typeof window.innerWidth != 'undefined') {
		viewportwidth = window.innerHeight;
	} else {
		viewportwidth = document.documentElement.clientHeight;
	}
	if ((viewportwidth > document.body.parentNode.scrollWidth) && (viewportwidth > document.body.parentNode.clientWidth)) {
		window_width = viewportwidth;
	} else {
		if (document.body.parentNode.clientWidth > document.body.parentNode.scrollWidth) {
			window_width = document.body.parentNode.clientWidth;
		} else {
			window_width = document.body.parentNode.scrollWidth;
		}
	}
	var popUpDiv = document.getElementById(popUpDivVar);
	window_width=window_width/2-150;//150 is half popup's width
	popUpDiv.style.left = window_width + 'px';
}

function popup(windowname) {
	blanket_size(windowname);
	window_pos(windowname);
	toggle('blanket');
	toggle(windowname);		
}