title: Set hidden form field values with JavaScript but request still empty
body: <p>I try to set some hidden form field values with an onclick event.
  Ok, after I did something like this:</p>
  
  <pre><code>document.getElementById('hidden_field').value = 123;
  </code></pre>
  
  <p>I can output the value with the firebug console by entering this:</p>
  
  <pre><code>alert(document.getElementById('hidden_field').value);
  </code></pre>
  
  <p>So the values are definitely set. But now when I submit the form, the hidden field values are still empty.</p>
  
  <p>Do you have any idea whats going wrong?</p>