function open_popup()
{
	$('screen').setStyles({
	display:'block',
	opacity: 0
	});
	
	$('screen').fade(0.7);
	
	$('popup-box').setStyles({
	display:'block',
	opacity: 0
	});
	
	$('popup-box').fade(1);
}

function close_popup()
{
	$('popup-box').fade(0);
	$('screen').fade(0);
}