body {
margin: 0;
}
#test {
width: 100%;
height: 100%;
position: absolute;
}
.content {
position: relative;
padding: 30px;
}
<svg id="test" viewBox="-250 0 500 300" preserveAspectRatio="xMidYMin slice">
<path fill="lightgrey" d="M-250,0C-250,0,-130,35,-91,51C-52,67,-23,78,-1,81C21,84,29,78,34,81C39,84,42,86,43,105C44,124,51,133,43,136C35,139,-30,103,-38,165C-46,227,75,207,127,208C179,209,239,212,257,236C257,266,257,296,257,326C88,326,-81,326,-250,326C-250,217.333,-250,108.667,-250,0z"/>
</svg>
<div class="content">
<h1>HTML Ipsum Presents</h1>
<p><strong>Pellentesque habitant morbi tristique</strong> senectus et netus et malesuada fames ac turpis egestas. Vestibulum tortor quam, feugiat vitae, ultricies eget, tempor sit amet, ante. Donec eu libero sit amet quam egestas semper. <em>Aenean ultricies mi vitae est.</em> Mauris placerat eleifend leo. Quisque sit amet est et sapien ullamcorper pharetra. Vestibulum erat wisi, condimentum sed, <code>commodo vitae</code>, ornare sit amet, wisi. Aenean fermentum, elit eget tincidunt condimentum, eros ipsum rutrum orci,
sagittis tempus lacus enim ac dui. <a href="#">Donec non enim</a> in turpis pulvinar facilisis. Ut felis.</p>
</div>