CSS for related posts http://www.wppicker.com/how-to-add-responsive-related-posts-without-plugin/

wpp-related-posts.css

 .wpp-related-list li {
  float: left;
  list-style-type: none;
  margin: 1%;
  text-align: center;
  width: 23%;
  border: 1px dotted #ccc;
  padding:6px;
}
 
.wpp-related-list img {
  display: block;
  margin: 0 auto;
  border: 1px dotted #ccc;
}

.wpp-clear{
	clear:both;
}

@media only screen and (max-width: 600px) {
	.wpp-related-list li {
		width:96%;
	}
}