<style>
  div.disclaimer {
    background-color: rgb(129, 0, 0);
    color: #fff;
    height: 6em;
    padding-left: 1em;
    padding-right: 1em;
    padding-bottom: 3px;
    padding-top: 5px;
    left: 0;
    position: absolute;
    right: 0;
    top: 0;
  }
</style>

<div class="disclaimer">
  <h3>DISCLAIMER</h3>
  <p>This Webapp is not yet ready for production and should not be relied on to be cryptographically secure</p>
</div>