Cursor doesn't work using cursor url?

Question

Second example work, the hand did show up, but why the first div doesn't work?

div {
  cursor: url('http://i.imgur.com/EuDeZWn.png'), auto;
}

span {
  cursor: url('http://www.javascriptkit.com/dhtmltutors/cursor-hand.gif'), auto;
}

<div>
  target
</div>
<br>
<br>
<span>
  target 2
</span>

Answer 1

From MDN:

In Gecko (Firefox) the limit of the cursor size is 128×128px. Larger cursor images are ignored. However, you should limit yourself to the size 32×32 for maximum compatibility with operating systems and platforms.

You image is 237 x 173, which is significantly larger.