ciao a tutti
sto cercando di far chiudere il tooltip da questa mia mappa ma non ci riesco, cosa posso fare?

codice:
<!DOCTYPE html>
<html lang="it">
<head>
   <title>Mappa</title>
   <meta name="viewport" content="initial-scale=1.0, user-scalable=no">
   <link href="inc/stile.css" rel="stylesheet" type="text/css">
   <style type="text/css">
html, body { margin:0; padding:0; width:80%; height:90%; }
body { background:#FFFFFF; color:#000000; font-family:Arial, Helvetica, sans-serif; font-size:12px; line-height:150%; text-align:center;}
#map { width:100%; height:100%; }
#tooltip { padding:10px; text-align:left; }
#tooltip p,  #tooltip img { float:left; display:inline; padding:0; margin:0 10px 0 0; }
</style>
   <script type="text/javascript" src="http://maps.google.com/maps/api/js?sensor=true&language=it"></script>
   <script type="text/javascript">
   var infowindow;
      var initialize = function() {
	  var latlng = new google.maps.LatLng(coordinatedellamappa); // centro della mappa
         var myLatlng = new google.maps.LatLng(coordinate del marker); // segnapunto
         // definizione della mappa
         var myOptions = {
             zoom: 13,
             center: latlng,
            mapTypeId: google.maps.MapTypeId.ROADMAP,
            mapTypeControlOptions: {style: google.maps.MapTypeControlStyle.HORIZONTAL_BAR}
         }
     var mymap = new google.maps.Map(document.getElementById('map'), myOptions); 
        
		 var marker = new google.maps.Marker(
		 {
            position: myLatlng,
            map: mymap,
			icon: 'gif/marker.png',
            flat: true
         });
		 
		 
		 
			 var tooltip = '<div id="tooltip">'+
	'<span class=hotel-ischia-nero>testo del tooltip</span>';
	'</div>';
	
    infowindow = new google.maps.InfoWindow({
        content: tooltip
    });
	
	    google.maps.event.addListener(marker, 'click', function() {
        infowindow.open(map,marker);
    });
	
      }
	  window.onload = initialize;
</script>
</head>
<body>
<div id="map"></div>
</body>
</html>