Google maps marker not showing up API v3

The marker isnt showing up, i read the docs but i cant find the problem, can somebody help me plz?

heres the js:

function initialize() {
      var mapOptions = {
        center: new google.maps.LatLng(-8.064903, -34.896872),
        zoom: 16,
        mapTypeId: google.maps.MapTypeId.ROADMAP
      };
      var map = new google.maps.Map(document.getElementById("map_canvas"), mapOptions);

      var marker = new google.maps.Marker({
          position: location,
          title:"Hello World!",
          visible: true
      });
      marker.setMap(map);
    }