How to distinguish between blank areas and non-blank areas in a webpage with JavaScript?
<p>How to distinguish between blank areas and non-blank areas in a webpage with JavaScript? Blank areas including:</p>

<ul>
<li>areas that are not occupied by DOM elements.</li>
<li>margins, borders and paddings of DOM elements.</li>
</ul>

<p>EDIT:<br>
As response to the first comment: I am working on a web-based ebook reader. Cursor is set to {cursor:move} for blank areas so that the user can drag and scroll the webpage.</p>
