index.html

<!DOCTYPE html>
<html>
  <head>
    <title>Data Science Seville</title>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>
    <link rel="shortcut icon" href="static/favicon.ico">
    <style type="text/css">
      html, body, div.horizontal {
        margin: 0;
        height: 100%;
        width: 100%;
      }

      body {
        background-color: #FAFAFA;
      }

      div.horizontal {
        display: flex;
        justify-content: center;
      }

      div.vertical {
        display: flex;
        flex-direction: column;
        justify-content: center;
      }

      .smaller {
        height: 400px;
        width: 400px;
      }
    </style>
  </head>
  <body>
    <div class="horizontal">
      <div class="vertical">
        <img class="smaller" src="static/dss_logo.png"/>
      </div>
    </div>
  </body>
</html>