title: How to get image source of first image with JQuery?
body: <p>In the following code, I want the first image to be displayed when the page loads, however, it doesn't show anything, and no error in Firebug.</p>
  
  <p>How can I get this line to work:</p>
  
  <pre><code>$('img#main').attr('src', $('img:first').src);
  </code></pre>
  
  <p><strong>Full Code:</strong></p>
  
  <pre><code>&lt;!DOCTYPE html&gt;
  &lt;html&gt;
      &lt;head&gt;
          &lt;script type="text/javascript" src="http://www.google.com/jsapi"&gt;&lt;/script&gt;
          &lt;script type="text/javascript"&gt;
              google.load('jquery', '1.5');
              google.setOnLoadCallback(function() {
  
                  $('img.thm').css({opacity: 0.7});
                  $('img#main').attr('src', $('img:first').src); //doesn't work
  
                  $('img.thm').width(80).click(function() {
                      $('img#main').attr('src', this.src);
                  });
                  $('img.thm').mouseover(function() {
                      $(this).css({opacity: 1.0});
                  });
                  $('img.thm').mouseout(function() {
                      $(this).css({opacity: 0.7});
                  });
              });
          &lt;/script&gt;
          &lt;style type="text/css"&gt;
              img.thm {
                  cursor: hand;
                  cursor: pointer;
              }
          &lt;/style&gt;
      &lt;/head&gt;
      &lt;body&gt;
          &lt;div id="menu"&gt;
              &lt;img class="thm" src="images/test1.png"/&gt;
              &lt;img class="thm" src="images/test2.png"/&gt;
              &lt;img class="thm" src="images/test3.png"/&gt;
          &lt;/div&gt;
          &lt;div id="content"&gt;
              &lt;img id="main"/&gt;
          &lt;/div&gt;
      &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>