title: leaflet.js map is not showing up
body: <p>I am a newbie to <code>leaflet.js</code>. Can anyone help me with debugging the following code? I am trying to show a map on screen but only zoom-in and zoom-out button  shows up on Google Chrome and the map screen is empty.</p>
  
  <pre><code>&lt;!DOCTYPE html&gt;
  &lt;html lang="en"&gt;
      &lt;head&gt;
          &lt;link rel="stylesheet" href="http://cdn.leafletjs.com/leaflet/v0.7.7/leaflet.css" /&gt;
          &lt;style&gt;
              #mapid { height: 180px; }
          &lt;/style&gt;
      &lt;/head&gt;
  
      &lt;body&gt;
          &lt;div id="mapid"&gt;&lt;/div&gt;
          &lt;script src="http://cdn.leafletjs.com/leaflet/v0.7.7/leaflet.js"&gt;&lt;/script&gt;
          &lt;script&gt;
              var mymap = L.map('mapid').setView([51.505, -0.09], 13);
          &lt;/script&gt;
      &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>