function show_lightbox()
{
	$('.lightbox').css('display','block');
	$('.lightbox .background').css('height', $(document).height());
	vertical_align($('.lightbox .body'));
}
function hide_lightbox()
{
	$('.lightbox').css('display','none');
}
function vertical_align(elem)
{
	$(elem).css('top', ($(window).height()-$(elem).height())/2+$(window).scrollTop());
}