function openVenster(url, t, w, h) 
	{
		var winlinks = (screen.width - w) / 2;
		var wintop = (screen.height - h) / 2;
		eval("page = window.open(url, 'popwin', 'toolbar=0,scrollbars=1,location=0,statusbar=1,menubar=0,resizable=1,width="+w+",height="+h+",left = "+winlinks+",top = "+wintop+"');");
		popwin.window.resizeTo(w,h);
		popwin.window.focus();
	}