title: jQuery hide all elements with the same id
body: <p>by topic I have some divs with id = "loader".</p>
  
  <p>In my jQuery code I have </p>
  
  <pre><code>  $("#loader").hide(),
  </code></pre>
  
  <p>but it works only with the first div.</p>
  
  <p>How could I hide all the divs?</p>
  
  <p>Thanks a lot.</p>