jquery表单验证插件
jQuery plugin: Validation
http://bassistance.de/jquery-plugins/jquery-plugin-validation/
http://docs.jquery.com/Plugins/Validation#Validator
api
http://docs.jquery.com/Plugins/Validation#Validator
demo
http://www.cnblogs.com/qiantuwuliang/archive/2009/08/03/1537213.html