JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.0/jquery.min.js"></script>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap-theme.min.css">
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
 <div class="site-wrapper">
        <div class="container">
            <div class="page-header">
                <img class="img-responsive" src="http://www.smoshmosh.com/images/startseite_logo.png"/>
            </div>
            <div class="page-body indexPageBody">
                <img class="img-responsive" src="http://www.smoshmosh.com/images/startseite_content.png"/>
                <div class="startButton">
                    <a id="startButton" href="dummyUrl"><img id="startButtonImg" class="img-responsive" src="http://www.smoshmosh.com/images/start_button.gif"/></a>
                </div>
            </div>
            <div class="page-footer">
                <img class="img-responsive" id="startseiteFooter" src="http://www.smoshmosh.com/images/startseite_footer.png"/>
                <button id="audioToggleButton" class="startAudio"><img id="musicImage" class="img-responsive" src="http://www.smoshmosh.com/images/music_on.png"/></button>
            </div>
        </div>
    </div>

CSS

body {
    margin-bottom: 0px;
    height: 100%;
}

.site-wrapper {
  position:relative;
}

.container {
    padding-left: 0;
    padding-right: 0;
    max-width: 500px;
    margin-bottom: 0px;
}

#audioToggleButton {
    float: left;
    z-index: 2;
}

button {
    border: 0;
    background-color: white;
}

button:focus {
    outline: none;
}

.site-wrapper:focus {
    outline: none;
}

.thumbnail {
    border: 0;
    box-shadow: none;
}

.carousel-inner>.item>a>img, .carousel-inner>.item>img, .img-responsive, .thumbnail a>img, .thumbnail>img {
    width: 100%;
    max-width: none;
}

.startButton {
    margin-top: 5%;
}

.page-header {
    border: 0;
    margin: 5% 5% 0 !important;
    padding-bottom: 0;
}

.page-body {
    min-height: 0;
}

.page-footer {
    max-width: 500px;
    position: absolute;
    bottom: 0;
}

.startAudio {
    position: absolute;
    bottom: 20%;
    left: 5%;
    background-color: transparent;
}

#musicImage {
    width: 30vw;
    max-width: 150px;
}

#startButtonImg {
    width: 45%;
    margin: 0 auto;
}

.indexPageBody {
    margin: 5% 5% 5% 5%;
}