how sticky-footer should be

with display: inline-block and position sticky

HTML

<a name="top"></a>
<header id="header">header-content</header>
<div class="contentWrapper">
  <main>
    <h1>Page-title</h1>
    <p>
      Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.
    </p>
    <h2>Sub-title</h2>
    <p>
      Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea <a href="https://jsfiddle.net">TRY TO CLICK ME</a> takimata sanctus est Lorem ipsum dolor sit amet.
    </p>
  </main>

  <!-- the way it SHOULT WORK -->
  <a href="#top" class="toTop-should-work">to top</a>

</div>

CSS

* {
  padding: 0;
  margin: 0;
  box-sizing: border-box;
}
#header {
  background: lightblue;
  padding: 50px;
  text-align: center;
}
main a {
  display: inline-block;
  padding: 5px 15px;
  background: lightgrey;
  
}

.contentWrapper {
  position: relative;
}

/*   how it should be */
.toTop-should-work {
  position: sticky;
  display: inline-block; /* this destroyes -the stick- */
  bottom: 2%;
  right: 2%; /* X-axes not supported? */
  padding: 10px;
  color: #fff;
  background: rgba(0,0,0,.5);
}