title: Making input field read only on the value of other input fields
body: <p>I want to make the input field read only on the base of other input field value, for example,</p>
  
  <pre><code>&lt;form action=""&gt;
  &lt;input type="radio" name="sex" value="male"&gt;Male&lt;br&gt;
  &lt;input type="radio" name="sex" value="female"&gt;Female &lt;br/&gt;
  Age: &lt;input type="text" name="age"&gt;&lt;br&gt;
  &lt;/form&gt;
  </code></pre>
  
  <p>If someone choose Female, then the age input should become read only, means that it should be fade out then no value can be entered. Is this possible, and how?</p>