.sample-img {
  width: 50px;
  height: 50px;
  background-image: url(https://foobar.cloudfront.net/images/sample.png);
}

.sample-img2 {
  width: 50px;
  height: 50px;
  background-image: url('https://foobar.cloudfront.net/images/sample.png');
}
