Lightweight jQuery Form Validation Plugin: Happy.js
There are various form validation plugins for jQuery and very good ones exist between them.
Many of them have lots of features and, if you are looking for a simplistic one, Happy.js can be a good alternative.
The plugin is lightweight and supports few input validations by default (required, date, number, e-mail, min/max and phone number). But it can be extended so easily by adding few lines and the regex for the rule you want.
Its styling in case of an error is smartly thought. Any non-validated elements get a custom class. Also, a
<span> element is added for each non-validated item so that an error text can be displayed.
And, Happy.js works with Zepto.js as well.