function popup (url,name,win_height,win_width)
		{
		pos_horizon = ((screen.width/2)-(win_width/2));
		pos_vertical = ((screen.height/2)-(win_height/2));
		window.open(url,name,"width="+win_width+",height="+win_height+",top="+pos_vertical+",left="+pos_horizon);
		}