In this fairly simple HTML page and CSS stylesheet, both the body and html elements are set to "height: 100%;" and yet the page is slightly longer than the window, creating a scrollbar that I don't want.
I've read through many stack exchange posts about this issue of extra space at the bottom of a page, but have not managed to find a fix or an explanation that works for me.
I am fairly certain that the problem is not being caused by a stray text node in the DOM. I have tried removing all extra white space in between tags in the HTML file to no avail. I have tried styling the body with "min-height: 100%", but then the purple content of the page no longer takes up 85% of the whole window as it did before. I have tried setting "overflow: hidden;" on the html element, which seems to work, but I have no idea why it does. I have even tried using a flexbox to achieve the functionality displayed in the code, but I haven't been able to make that work either.
When I right click on that extra unwanted yellow space on the bottom and click "Inspect Element" I get directed to a "buttonWrapper" div, but I have no idea why this would be causing any problems.
A valid explanation of why this is happening is more important to me than a solution right now (hence my dissatisfaction with the "overflow: hidden;" method). If you do have a solution, I'd prefer it would be entirely CSS based.
Thanks for taking the time to read this.
* {
  margin: 0;
  padding: 0;
}
html {
  background-color: yellow;
  width: 100%;
  height: 100%;
}
body {
  background-color: grey;
  width: 100%;
  height: 100%;
}
#titleSection {
  width: 100%;
  height: 15%;
  text-align: center;
  font-size: 10vmin;
}
#contentSection {
  width: 100%;
  height: 85%;
  background-color: purple;
}
.buttonWrapper {
  width: 50%;
  height: 100%;
  display: inline-block;
}
.buttonImage {
  height: 100%;
  width: 100%;
  object-fit: contain;
}
<!doctype html>
<html>
<head lang="en">
  <meta charset="utf-8">
  <title></title>
  <link type="text/css" rel="stylesheet" href="style.css">
  <link rel="icon" href="" type="image/x-icon" />
  <script src="code.js"></script>
</head>
<body>
  <div id="titleSection">Who's going to set up the board?</div>
  <div id="contentSection">
    <div class="buttonWrapper">
      <img src="http://orig15.deviantart.net/7e51/f/2013/293/e/9/owl_face_by_cypher2-d6r9e23.png" class="buttonImage">
    </div><!--
  
 --><div class="buttonWrapper">
      <img src="http://eredivisiezeilen.nl/wp-content/uploads/2015/04/1429207962_male3-512.png" class="buttonImage">
    </div>
  </div>
</body>
</html>