<div>'s have height and width, not length. Here is an example of a <div> that has a fixed width and a height that auto-adjusts based upon the content, which are text quotations of various lengths.
<div id="id01" style="width:300px;min-height:300px;padding:5px 5px 20px 5px;background-color:#ddd;box-shadow:3px 3px 8px #000 inset,-5px -5px 8px #000 inset"></div>
Note that there's a minimum height - An esthetic adjustment.
This should get you on your way.