Basic HTML5 Input (placeholder and required) Polyfill/Shim Loader using Modernizr.

html5_input_polyfill.js

//defer until Modernizr is loaded.
$(function () {

    /* HTML5 Input Placeholder Polyfill. */
    Modernizr.load({
        test: Modernizr.input.placeholder,
        nope: [
            '/assets/css/placeholder_polyfill.min.css',
            '/assets/js/placeholder_polyfill.jquery.min.combo.js'
        ]
    });

    /* Basic HTML5 Input Validation	Polyfill.
     * right now, we're only testing for required. if more
     * HTML5 goodness is used, additional yepnope testers
     * may be required. the library below covers multiple
     * features, Check out http://ericleads.com/h5validate/
     */
    Modernizr.load({
        test: Modernizr.input.required,
        nope: [
            '/assets/js/jquery.h5validate.js'
        ]
    });

});

//initialize h5Validation polyfill
$(document).ready(function () {
    //make sure h5Validate is loaded properly
    if (typeof jQuery.h5Validate != 'undefined') $('form').h5Validate({
        //custom error CSS class to use for "required" inputs
        errorClass: "required_field"
    });
});