function popup(parameter)
{
	popupsize_x = 640;
	popupsize_y = 480;
	popup_fenster = window.open("about:blank", "Bild", "width="+popupsize_x+", height="+popupsize_y);
	//FENSTERBREITE
	windowwidth = screen.width;
	windowheight = screen.height;

	mitte_x = (windowwidth/2) - (popupsize_x/2);
	mitte_y = (windowheight/2) - (popupsize_y/2);
	popup_fenster.focus();
	popup_fenster.location.href = "../showpicture.asp?" + parameter;
	popup_fenster.moveTo(mitte_x,mitte_y);
}