Code to navigate to previous page in history if under same domain

JS onclick="history.go(-1) only if under my domain

<script>
    function backClick() {
      if(document.referrer.indexOf('mysite.com') >= 0) {
       history.go(-1);
      }
      else {
       window.location.href = 'myHomePageUrl'; // this might just be '/' of your site
      }
      return false;
    }
</script>
<br/><a href="" onclick="backClick()">close</a>

Source: https://stackoverflow.com/a/19417145