w3cvalidator.js

var W3CValidator = (function() {
    var W3CURL = "http://validator.w3.org/check";
    
    return {
        validate:function(str,cb) {
            $.post(W3CURL, {
                "fragment":str,
                "output":"json"
            }, function(res,code) {
                cb(res);
            });
        }
    };
}());