title: JQuery Validation Plugin: valid() returns false for non-required fields
body: <p>The valid() function states:
  "Checks whether the selected form is valid or whether all selected elements are valid."</p>
  
  <p>Which seems to imply we can test for a group of controls using a selector (we're testing controls on a asp.net form) e.g.</p>
  
  <pre><code>$('div[id$=pnlBillingInfo] .Field input').valid()
  </code></pre>
  
  <p>This works if all fields are required.  However, if one field requires no validation (required = false) then valid() returns false when this field is left blank.</p>
  
  <p>This behavior doesn't seem correct - are we missing something?  We should be able to leave these optional fields blank and still have the group of controls validate ok.</p>
  
  <p>If we try to validate this optional field - the result is 'undefined' e.g.</p>
  
  <pre><code>$("#aspnetForm").validate().element('input[id$=txtBillingAddress2]')
  </code></pre>
  
  <p>jQuery 1.4.2</p>
  
  <p>jQuery plugin Validation 1.7 (latest version)</p>
  
  <p><a href="http://bassistance.de/jquery-plugins/jquery-plugin-validation/" rel="nofollow noreferrer">http://bassistance.de/jquery-plugins/jquery-plugin-validation/</a></p>
  
  <p>Thanks!</p>