title: how to fix failure of scroll attribute on CSS overflow property
body: <p>I'm trying to include a large image (a map) as background in a web page, with the ability to scroll to view the areas outside the current viewport. I'm using the CSS overflow property and its scroll attribute. 'Scroll' attribute on the CSS 'overflow' property fails. The borders appear on the right and bottom of the browser window, but without scrollbars. As a result it is not possible to scroll the HTML element. Desired behavior is functional scroll bars. </p>
  
  <p>I tried switching the sequence of the CSS properties, understanding that the last one rules. No impact. Tried viewing in different browsers, to see if it's browser-specific. Fails equally in Firefox, Chrome, Chromium, and Safari. MDN docs indicate this should work. </p>
  
  <p>...</p>
  
  <pre><code>&lt;style type="text/css"&gt;
  html {
    background-image: url(art/GbMap.png);
    background-size: 2000px 2100px;
    overflow: scroll;
  }
  &lt;/style&gt;
  </code></pre>
  
  <p>...</p>
  
  <p>Expected: borders on the bottom and right with scrollbars that allow me to scroll the image.
  Actual: borders on the bottom and right, but no scrollbars.</p>