Want to validate a form with jQuery but it keeps on submitting
<?php
         include 'connect.php';
         include 'header.php';

                echo '<h2>Register</h2>';
                echo '
                <div class="container">
                    <form id="submit" method="post" name="submit">
                        <fieldset>
                            <legend> Enter Information </legend>
                                <br/>
                                    <p><label for="user_name">Your username: </label>
                                <br/>
                                    <input id="user_name" class="text" name="user_name" size="20" type="text" placeholder="Your name"></p>
                                    <p><label for="user_pass">Your password: </label>
                                <br/>
                                    <input id="user_pass" class="text" name="user_pass" size="20" type="password" placeholder="Your password"></p>

                                    <p><label for="user_pass_check">Confirm password: </label>
                                <br/>
                                    <input id="user_pass_check" class="text" name="user_pass_check" size="20" type="password" placeholder="Confirm your password"></p>


                                    <p><label for="user_email">Email: </label>
                                <br/>
                                    <input id="user_email" class="text" name="user_email" size="20" type="text" placeholder="E.g. mail@mail.com"></p>
                                <br/>
                                    <button class="button positive" type="submit"> <img src="like.png" alt=""> Register </button>
                        </fieldset>
                    </form>
                <div class="success" style="display: none;"> You are now a registered user!</div>
                </div>';
?>

$(document).ready(function(){
      $("#formid").submit(function(e) {

            var user_name = $('#user_name').val();
            var user_email = $('#user_email').val();
            var user_pass = $('#user_pass').val();

            $.ajax({
                    type: "POST",
                    url: "ajax.php",
                    data: "user_name="+ user_name + "&user_email=" + user_email + "&user_pass=" + user_pass,
                    success: function(){
                        $('form#submit').hide(function(){$('div.success').fadeIn();});
                    }
            });

            e.preventDefault()
            return false;
      });

});

$(document).ready(function()
{
    $("#formid").submit(function(e)
    {
        e.preventDefault();
        var error = false;

        $("#submit p input")
        .removeClass('error')
        .next('span')
        .remove();

        $(this).find(":text").each(function()
        {
            if ($(this).val().length == 0)
            {
                $(this).addClass('error')
                .after('<span class="error"> This field must have a value </span>');
                error = true;
            }
            else if ($(this).attr('id') == "user_email")
            {
                var theTest = $(this).val().toString();
                if (theTest.indexOf('@') == -1)
                {
                    $(this).removeClass('error')
                    .next('span')
                    .remove();

                    $(this).addClass('error')
                    .after('<span class="error"> This field must be a valid email </span>');
                    error = true;
                }
                else if (theTest.indexOf('.') == -1)
                {
                    $(this).removeClass('error')
                    .next('span')
                    .remove();

                    $(this).addClass('error')
                    .after('<span class="error"> This field must be a valid email </span>');
                    error = true;
                }
                else
                {
                    $(this).removeClass('error')
                    .next('span')
                    .remove();
                }
            }
            else
            {
                $(this).removeClass('error')
                .next('span')
                .remove();
            }
        });

        $(this).find(":password").each(function()
        {
            if ($(this).val().length == 0)
            {
                $(this).addClass('error')
                .after('<span class="error"> This field must have a value </span>');
                error = true;
            }
            else
            {
                $(this).removeClass('error')
                .next('span')
                .remove();
            }
        });

        if (error)
        {
            e.preventDefault();
            return false;
        }
        return true;
    });
}
);

$(document).ready(function(){

      $("form#submit").submit(function(e) {

        e.preventDefault();
        var error = false;

        $("#submit p input")
        .removeClass('error')
        .next('span')
        .remove();

        $(this).find(":text").each(function()
        {
            if ($(this).val().length == 0)
            {
                $(this).addClass('error')
                .after('<span class="error"> This field must have a value </span>');
                error = true;
            }
            else if ($(this).attr('id') == "user_email")
            {
                var theTest = $(this).val().toString();
                if (theTest.indexOf('@') == -1)
                {
                    $(this).removeClass('error')
                    .next('span')
                    .remove();

                    $(this).addClass('error')
                    .after('<span class="error"> This field must be a valid email </span>');
                    error = true;
                }
                else if (theTest.indexOf('.') == -1)
                {
                    $(this).removeClass('error')
                    .next('span')
                    .remove();

                    $(this).addClass('error')
                    .after('<span class="error"> This field must be a valid email </span>');
                    error = true;
                }
                else
                {
                    $(this).removeClass('error')
                    .next('span')
                    .remove();
                }
            }
            else
            {
                $(this).removeClass('error')
                .next('span')
                .remove();
            }
        });

        $(this).find(":password").each(function()
        {
            if ($(this).val().length == 0)
            {
                $(this).addClass('error')
                .after('<span class="error"> This field must have a value </span>');
                error = true;
            }
            else
            {
                $(this).removeClass('error')
                .next('span')
                .remove();
            }
        });

        if (error)
        {
            e.preventDefault();
            return false;
        }


        var user_name = $('#user_name').val();
        var user_email = $('#user_email').val();
        var user_pass = $('#user_pass').val();

        $.ajax({
             type: "POST",
             url: "ajax.php",
             data: "user_name="+ user_name + "&user_email=" + user_email + "&user_pass=" + user_pass,
             success: function(e){
                 if(!error){
                    $('form#submit').hide(function(){$('div.success').fadeIn();});
                 }
             }
        });
    });
      return true;
});

$("form#submit").submit(function(e) {
    e.preventDefault();
    ...

event.preventDefault();

$('#formid').submit();