使用视差滚动后，链接无法点击

Question

我一直在为学校制作这个网站，我想我会弄清楚视差滚动是如何工作的。所以我开始使用最简单的教程来准确地说明one。在我这样做后，我放置了导航栏。我记得当时工作正常，但在响应后我没有检查，现在我不能再点击链接了。 这是我的HTML：

            <div id="group2" class="parallax_group">
            <!-- <div class="parallax_layer parallax_layer-back">
                                                                                                background
            </div> -->
            <div class="parallax_layer parallax_layer-base">
                <div id="nav" class="nav">
                    <ul>
                        <li><a class="active" href="#">Home</a></li>
                        <li><a href="about.html">Over ons</a></li>
                        <li><a href="#">Wat leveren wij?</a></li>
                        <li><a href="#">Contact</a></li>
                        <li><a href="#">Demo</a></li>
                    </ul>
                </div>
                <div class="section group">
                    <div class="col span_1_of_3">
                        <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Quibusdam id nam, necessitatibus at odit nobis vitae, dolor sequi sunt doloremque minima, debitis. Sed debitis possimus esse soluta mollitia est culpa.</p>
                    </div>
                    <div id="middle" class="col span_1_of_3">
                        <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Qui autem impedit, a, error accusantium soluta molestias quidem quo totam beatae eligendi sint, modi voluptatem nemo fugiat recusandae ullam consequatur nihil?</p>
                    </div>
                    <div class="col span_1_of_3">
                        <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Provident voluptatibus, quaerat nostrum ullam distinctio praesentium! Nemo eveniet provident id, tenetur cumque natus, quas porro possimus maiores, minus amet laboriosam ea?</p>
                    </div>
                </div>
            </div>
        </div>

这是我的css：

* {
    padding: 0;
    margin: 0;
}
body {
    text-align: center;
}
h1{
    display: inline-block;
    font-family: 'Raleway', sans-serif;
    color: white;
    text-shadow: -1px 0 black, 0 1px black, 1px 0 black, 0 -1px black;
}
p{
    display: inline-block;
    font-family: 'Raleway', sans-serif;
    color: black;
}
header {
    z-index: 5;
    line-height: 100vh;
}
header .parallax_layer-back {
    background: url(sample.jpg);
    background-size: contain;
    background-repeat: no-repeat;
}
#group2 {
    z-index: 3;
}
#group2 .parallax_layer-base {
    background-color: #dbdbdb;
}
.parallax {
    perspective: 300px;
    height: 100vh;
    overflow-x: hidden;
    overflow-y: auto;
}
.parallax_layer {
    position: absolute;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
}
.parallax_layer-base {
    transform: translateZ(0px);
    z-index: 4;
}
.parallax_layer-back {
    transform: translateZ(-300px) scale(2);
    z-index: 3;
    height: 150vh;
}
.parallax_layer-deep{
    transform: translateZ(-600px) scale(3);
    z-index: 2;
    background-color: #dbdbdb;
}
.parallax_group {
    position: relative;
    height: 100vh;
    transform-style: preserve-3d;
    /*transform: translate3d(700px, 0, -800px) rotateY(30deg);*/
}
/*Columns*/

/*  SECTIONS  */
.section {
    clear: both;
    padding: 0px;
    margin: 0px;
}

/*  COLUMN SETUP  */
.col {
    display: block;
    float:left;
    margin: 1% 0 1% 1.6%;
}
.col:first-child { margin-left: 0; }


/*  GROUPING  */
.group:before,
.group:after {
    content:"";
    display:table;
}
.group:after {
    clear:both;
}
.group {
    zoom:1; /* For IE 6/7 */
}

/*  GRID OF THREE  */
.span_3_of_3 {
    width: 100%;
}
.span_2_of_3 {
    width: 66.1%;
}
.span_1_of_3 {
    width: 32.2%;
}
#middle{
    border-top: 0px;
    border-bottom: 0px;
    border-right: 1px;
    border-left: 1px;
    border-style: solid;
}

/*navigation*/

.nav {
    position: sticky;
    top: 0px;
    height: 100px;
    width: 100%;
    z-index: 30;
    font-family: 'Raleway', sans-serif;
    font-size: 20px;
    background-color: #dbdbdb;
}
.nav ul {
    list-style-type: none;
    margin-left: 0;
    padding-top: 40px;
    font-size: 25px;
    font-family: 'Raleway', sans-serif;
    line-height: 0;
    z-index: 30;
}
.nav li {
    display: inline-block;
    margin-left: 15px;
    padding-bottom: 25px;
    z-index: 30;

}
a:link {
    color: #2F649B;
    font-family: inherit;
}
a:visited {
    color: #2F649B;
}
a:hover {
    color: #6D92B9;
    text-decoration: none;
}
a:active {
    color: #26507C;
    text-decoration: none;
}
footer {
    position: sticky;
    bottom: 0px;
    height: 100px !important;
    line-height: 100px;
    width: 100%;
}

我知道这是一堆代码，但我不知道它是什么，所以我继续前进并给了你一切。 编辑：其他html视差组：

<!DOCTYPE html>
<html>
    <head>
        <title>Squirel WebDesign</title>
        <link rel="stylesheet" type="text/css" href="main.css">
        <link rel="stylesheet" type="text/css" href="handheld.css" media="screen and   (max-device-width: 480px), screen and (max-width: 480px)">
    </head>
    <body>
        <div class="parallax">
            <header class="parallax_group">
                <div class="parallax_layer parallax_layer-base">
                    <h1>i'm a bloody big header preferably with a squirel</h1>
                </div>
                <div class="parallax_layer parallax_layer-back">
                </div>
                <div class="parallax_layer parallax_layer-deep">
                </div>
            </header>