Source

<html>
  <head>
    <title>Step 1: A Simple Map</title>
    <script src="../OpenLayers.js"></script>
    <script src="../OpenStreetMap.js"></script>
    <script>
      function init() {
        map = new OpenLayers.Map("demoMap");
        map.addLayer(new OpenLayers.Layer.OSM.Mapnik());
        map.zoomToMaxExtent();
      }
    </script>
  </head>
  <body onload="init();">
    <div id="demoMap"></div>
  </body>
</html>