title: Why can't I use "required" and "disabled" at the same time in radio input field?
body: <p>I want to add <code>required</code> property in radio input field and here is my code </p>
  
  <pre><code>&lt;!doctype html&gt;
  &lt;html&gt;
      &lt;head&gt;
          &lt;meta charset='utf-8'&gt;
          &lt;title&gt;test radio&lt;/title&gt;
          &lt;style&gt;
              div.radio{
                  background-color:silver;
              }
          &lt;/style&gt;
      &lt;/head&gt;
      &lt;body&gt;
          &lt;form action='procesPost.html' method='POST'&gt;
              &lt;div class='radio'&gt;
                  &lt;input type='radio' required name='test' value=1&gt;
                  &lt;input type='radio' required name='test' value=2&gt;
              &lt;/div&gt;
              &lt;input type='SUBMIT' value='submit'&gt;
          &lt;/form&gt;
      &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>It works well,I have to select one radio to submit, However, if I want to disable one radio, the <code>required</code> constraint will not work</p>
  
  <pre><code>&lt;!doctype html&gt;
  &lt;html&gt;
      &lt;head&gt;
          &lt;meta charset='utf-8'&gt;
          &lt;title&gt;test radio&lt;/title&gt;
          &lt;style&gt;
              div.radio{
                  background-color:silver;
              }
          &lt;/style&gt;
      &lt;/head&gt;
      &lt;body&gt;
          &lt;form action='procesPost.html' method='POST'&gt;
              &lt;div class='radio'&gt;
                  &lt;input type='radio' required name='test' value=1&gt;
                  &lt;input type='radio' required disabled name='test' value=2&gt;
              &lt;/div&gt;
              &lt;input type='SUBMIT' value='submit'&gt;
          &lt;/form&gt;
      &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>Now, I can submit the form even though I didn't select any radio.
  I wonder why this would happen and how could I solve this problem?</p>
  
  <p>I tested my code in FierFox 32.0.3, RHEL6.2</p>