How to validate node title field Drupal 7 I want to add validation to the node title field. When the user enters the character X and submits the form they should get a message saying "you are not allowed to enter special character X".
You can setup field/property validations with the module Field validation.

Here's the documentation on how to add validation to properties (with the Field validation module), as the title isn't a field in Drupal 7.