title: jQuery validation either no value or length of 4 characters
body: <p>I would like to know if it's possible to set the jQuery validate properties to either skip validation if there is no value in the textbox or if there is some value then the value should be exactly 4 characters.</p>
  
  <p>Something like:</p>
  
  <pre><code>txtObject: {
                       //put validation properties here
                      },
  </code></pre>
  
  <p>Is that possible?</p>