title: Jquery matching multiple elements with same id/class
body: <p>I am working on showing a message when a particular element has a width of less than 50, however there are multiple elements with the same class and only the first element in the page is displaying the message. here is the jsfiddle <a href="http://jsfiddle.net/MaNdn/23/" rel="nofollow">http://jsfiddle.net/MaNdn/23/</a></p>
  
  <p>Here is the function.</p>
  
  <pre><code>function checkads() {
      if ($('#container').height() &lt; 50) {
          $('#container').parent().parent().prepend('&lt;div id="ad-notice"&gt;Please support our website&lt;/div&gt;');
      //
  }
  }
  
  $(document).ready(checkads);
  </code></pre>
  
  <p>My question is, how do you make the message prepend to all element id instances found. I have various advertisements around my website, they are all wrapped in an div element named <code>advertisement_container</code> then how do I match them all at once</p>