The jQuery ht5ifv plugin is an extensible and highly configurable jquery plugin which allows validation of the HTML5's forms while the user is typing.

It is extensible because it allows the programmer to define new restrictions beyond those already defined by HTML5.

It is highly configurable because not only does it allow changes to the validation rules defined by HTML5, but also the addition of new ones.

Moreover, although assuming, by default, behaviors and ways to flag the errors in a very intuitive manner, it also provides the developer with complete freedom to redefine or even suppress them.

It give HTML5 form validation even if the browser does not yet suport them natively.

How to use it

<script 
    src="http://ajax.googleapis.com/ajax/libs/jquery/1.6.2/jquery.min.js " 
    type="text/javascript" 
    charset="UTF-8">
</script>

<link 
    rel="stylesheet" 
        type="text/css" 
        media="screen" 
        href="http://serprest.pt/jquery/ht5ifv.css "/>

<script 
    type="text/javascript" 
    src="http://serprest.pt/jquery/jquery.ht5ifv.js " 
    charset="UTF-8">
</script>

<script type="text/javascript" charset="UTF-8">      
    $(document).ready(function(){
        $('form').ht5ifv();
    });
</script>

For more details and options see the documentation available from http://serprest.pt/jquery/ht5ifv/docs/docs.html and from http://paginas.fe.up.pt/~jvv/jquery/ht5ifv/docs/docs.html