jQuery Inline Form Validation Engine | Web Resources | WebAppers
http://www.webappers.com/2009/06/12/jquery-inline-form-validation-engine/

jQuery Inline Form Validation Engine - Open Source Resources for Web Developers

alternate jquery validation plugin

jQuery.validity is an elegant and powerful jQuery plug-in you can use to setup client-side form validation. Instead of writing validation manually or balancing some unwieldy server-side framework, validity allows you to design client-side validation in a manner that feels natural and straightforward.