Is there a way to remove the horizontal and vertical space between the squares?
<div class="first">
<ul>
<li><img src="http://dummyimage.com/40x40/111111/000000.jpg"/></li>
<li><img src="http://dummyimage.com/40x40/222222/000000.jpg"/></li>
<li><img src="http://dummyimage.com/40x40/333333/000000.jpg"/></li>
<li><img src="http://dummyimage.com/40x40/444444/000000.jpg"/></li>
</ul>
</div>
<div class="first">
<ul>
<li><img src="http://dummyimage.com/40x40/555555/000000.jpg"/></li>
<li><img src="http://dummyimage.com/40x40/666666/000000.jpg"/></li>
<li><img src="http://dummyimage.com/40x40/777777/000000.jpg"/></li>
<li><img src="http://dummyimage.com/40x40/888888/000000.jpg"/></li>
</ul>
</div>