</div>
    </div>
</body>
</html> A simple page is centered so that the picture inside can be scrolled. Then I manually use scale on the page to enlarge the picture, the parent element of the enlarged image  content  can not adapt to the height, but I reset the overflow property of content to the page to adapt to the height of the picture, so that it can be scrolled. 
what is the principle of this?
