Edit in JSFiddle

/**************************************
* Recreación de la galería de Apple y el uso que hace de box-shadow
* SÓLO A EFECTOS DIDACTICOS para artículo del blog divulgativo
* de CSS
 **************************************/ 
.promos {
  width: 980px;
  margin: 1rem auto;
}
.promos ul {
  list-style-type: none;
  padding: 0;
}
.promos li, .promos a, .promos img {
  border-radius: 5px;
}
.promos li {
  float: left;
  position: relative;
  border-top: 1px solid #F2F2F2;
  box-shadow: rgba(0, 0, 0, 0.15) 0 1px 3px;
  margin-left: 11px;
}
.promos li:first-child {
  margin-left: 0;
}
.promos li:last-child {
  margin-left: 10px;
}
.promos a, .promos img {
  display: block;
}
.promos a {
  box-shadow: 0 -3px 1px rgba(255, 255, 255, 0.6), inset 0 2px 1px rgba(255, 255, 255, 0.97), 0 0 3px -1px rgba(0, 0, 0, 0.7);
  background-color: #f0f0f0;
  *zoom: 1;
  filter: progid:DXImageTransform.Microsoft.gradient(gradientType=0, startColorstr='#FFF9F9F9', endColorstr='#FFF0F0F0');
  background-image: -webkit-gradient(linear, 50% 0%, 50% 100%, color-stop(50%, #f9f9f9), color-stop(100%, #f0f0f0));
  background-image: -webkit-linear-gradient(top, #f9f9f9 50%, #f0f0f0 100%);
  background-image: -moz-linear-gradient(top, #f9f9f9 50%, #f0f0f0 100%);
  background-image: -o-linear-gradient(top, #f9f9f9 50%, #f0f0f0 100%);
  background-image: linear-gradient(top, #f9f9f9 50%, #f0f0f0 100%);
}
.promos a:hover {
  background-color: #f6f6f6;
  *zoom: 1;
  filter: progid:DXImageTransform.Microsoft.gradient(gradientType=0, startColorstr='#FFF9F9F9', endColorstr='#FFE0E0E0');
  background-image: -webkit-gradient(linear, 50% 0%, 50% 100%, color-stop(50%, #f9f9f9), color-stop(100%, #e0e0e0));
  background-image: -webkit-linear-gradient(top, #f9f9f9 50%, #e0e0e0 100%);
  background-image: -moz-linear-gradient(top, #f9f9f9 50%, #e0e0e0 100%);
  background-image: -o-linear-gradient(top, #f9f9f9 50%, #e0e0e0 100%);
  background-image: linear-gradient(top, #f9f9f9 50%, #e0e0e0 100%);
}
.promos a:hover .play {
  opacity: 1;
  background-position: left bottom;
}
.promos .curve-down {
  box-shadow: 0 8px 3px -5px rgba(0, 0, 0, 0.2);
  border-radius: 100%/32px;
}
.promos .play {
  width: 46px;
  height: 46px;
  position: absolute;
  left: 95px;
  top: 70px;
  opacity: .8;
  background: url(http://dl.dropbox.com/u/15746367/images/video_play_medium.png) 0 0 no-repeat;
  opacity: 0.8;
}

.clearfix:before, .clearfix:after {
  content: " ";
  display: table;
}
.clearfix:after {
  clear: both;
}

<aside class="promos">
	<ul class="clearfix">
		<li>
    <div class="curve-down">
			<a class="promo1" href="#">
        <img src="http://dl.dropbox.com/u/15746367/images/promo_ipad_mini.png" alt="iPad mini. Every inch an iPad." width="237" height="185">
      </a>
		</div>
    </li>
    
		<li><div class="curve-down">
			<a class="promo2" href="#"><img src="http://dl.dropbox.com/u/15746367/images/promo_imac.png" alt="The new iMac." width="237" height="185"></a>
		</div></li>	
    
		<li><div class="curve-down">
			<a class="promo3" href="#"><img src="http://dl.dropbox.com/u/15746367/images/promo_iphone5.png" alt="iPhone 5. The biggest thing to happen to iPhone since iPhone." width="237" height="185"></a>
		</div></li>
    
		<li><div class="curve-down">
			<a class="promo4" href="#"><span class="play"></span><img src="http://dl.dropbox.com/u/15746367/images/promo_iphone_ad.png" alt="Watch the new iPhone TV ad." width="237" height="185"></a>
		</div></li>
    
	</ul>
</aside>