Active Navigation Links on Scroll

This code adds the class "active" to the <a> tags with the class "link" when the element with the same ID as the HREF value is reached.

HTML

<header>
    <nav>
        <ul>
            <li><a class="link active" href="#section_one">Section One</a>
            </li>
            <li><a class="link" href="#section_two">Section Two</a>
            </li>
            <li><a class="link" href="#section_three">Section Three</a>
            </li>
        </ul>
    </nav>
</header>
<section id="section_one"></section>
<section id="section_two"></section>
<section id="section_three"></section>

CSS

/* RESET CSS */
 * {
    margin: 0;
    padding: 0;
    border: 0;
    font-family: Calibri;
    font-size: 100%;
    vertical-align: top;
    box-sizing:border-box;
    -moz-box-sizing:border-box;
    -webkit-box-sizing:border-box;
}
/* MY STYLES */
 html, body {
    height: 100%
}
header {
    background: #CCCCCC;
    position: fixed;
    left: 0px;
    top: 0px;
    height: 40px;
    width: 100%
}
nav {
    text-align: center;
}
nav ul {
    display: inline-block;
    text-align: center;
}
nav ul li {
    float: left;
    line-height: 40px;
    list-style-type: none;
    padding: 0px 10px;
}
nav ul li a {
    color: #999999;
    text-decoration: none;
}
nav ul li a.active {
    color: #222222;
    text-decoration: underline;
}
section {
    min-height: 100%;
    width: 100%;
}
#section_one {
    background: #BBBBBB;
    padding-top: 40px;
}
#section_two {
    background: #999999;
}
#section_three {
    background: #777777;
}

JavaScript

// ADDS ACTIVE CLASS TO LINKS WHEN SECTION WITH THE SAME SELECTOR AS THE HREF IS REACHED (CLASS .LINK IS NEEDED ON ALL <a> TAGS)

$(document).ready(function () {
    $(window).scroll(function () {

        var y = $(this).scrollTop();

        $('.link').each(function (event) {
            if (y >= $($(this).attr('href')).offset().top - 40) 						{
                $('.link').not(this).removeClass('active');
                $(this).addClass('active');
            }
        });

    });
});

// SMOOTH SCROLLING (with negative scroll of 40 for header)

/* $(function () {
    $('a[href*=#]:not([href=#])').click(function () {
        if (location.pathname.replace(/^\//, '') == this.pathname.replace(/^\//, '') && location.hostname == this.hostname) {
            var target = $(this.hash);
            target = target.length ? target : $('[name=' + this.hash.slice(1) + ']');
            if (target.length) {
                $('html,body').animate({
                    scrollTop: (target.offset().top - 40)
                }, 850);
                return false;
            }
        }
    });
}); */