Ajax-validation-function.md

• Elements of ajax validation
  See http://drupalconnect.com/blog/drupal-ajax-form-validation

1. a form define in the .module
2. in this form definition, drupal_add_js to add the validation javascript
3. in the js file, make a jquery listener, that call an url in ajax
4. the url is defined in a hook menu and point to a callback function.
5. depending of the reponse the js part print a message to the user