/* http://www.pat-burt.com/web-development/how-to-do-a-css-popup-without-opening-a-new-window/ */

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 ((viewportheight > document.body.parentNode.scrollHeight) && (viewportheight > document.body.parentNode.clientHeight)) {
	blanket_height = viewportheight;
    } else {
	if (document.body.parentNode.clientHeight > document.body.parentNode.scrollHeight) {
	    blanket_height = document.body.parentNode.clientHeight;
	} else {
	    blanket_height = document.body.parentNode.scrollHeight;
	}
    }
    var blanket = document.getElementById('blanket');
    blanket.style.height = blanket_height + 'px';
    var popUpDiv = document.getElementById(popUpDivVar);
    popUpDiv_height=blanket_height/2-150;//150 is half popup's height
    popUpDiv.style.top = popUpDiv_height + '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);
}