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 popup_background_size(popup_windowVar) {
	if (typeof window.innerWidth != 'undefined') {
		viewportheight = window.innerHeight;
	} else {
		viewportheight = document.documentElement.clientHeight;
	}
	if ((viewportheight > document.body.parentNode.scrollHeight) && (viewportheight > document.body.parentNode.clientHeight)) {
		popup_background_height = viewportheight;
	} else {
		if (document.body.parentNode.clientHeight > document.body.parentNode.scrollHeight) {
			popup_background_height = document.body.parentNode.clientHeight;
		} else {
			popup_background_height = document.body.parentNode.scrollHeight;
		}
	}
	var popup_background = document.getElementById('popup_background');
	popup_background.style.height = popup_background_height + 'px';
	var popup_window = document.getElementById(popup_windowVar);
	//popup_window_height=popup_background_height/2-250;//150 is half popup's height
	//popup_window.style.top = popup_window_height + 'px';
}
function window_pos(popup_windowVar, popup_width) {
	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;
		}
	}
	if(!popup_width) {
	  popup_width = 240;
	} else {
	  popup_width = popup_width / 2;
	}
	var popup_window = document.getElementById(popup_windowVar);
	window_width=window_width/2-popup_width;
	popup_window.style.left = window_width + 'px';
}
function popup(windowname, popup_width) {
	popup_background_size(windowname);
	window_pos(windowname, popup_width);
	toggle('popup_background');
	toggle(windowname);		
	scroll(0, 0);
}