Demo de funcionamiento con el flexbox, ver mas info: http://css-tricks.com/snippets/css/a-guide-to-flexbox/

demo-flex-css.html

<ul class="flex-container">
  <li class="flex-item">1</li>
  <li class="flex-item">2</li>
  <li id="pepito" class="flex-item">3</li>
  <li class="flex-item">4</li>
  <li class="flex-item">5</li>
  <li class="flex-item">6</li>
   <li class="flex-item">7</li>
  <li class="flex-item">8</li>
  <li class="flex-item">9</li>
  <li class="flex-item">10</li>
  <li class="flex-item">11</li>


</ul>

style.css

.flex-container {
  padding: 0;
  margin: 0;
  list-style: none;
  
  display: -webkit-box;
  display: -moz-box;
  display: -ms-flexbox;
  display: -webkit-flex;
  display: flex;
  
  -webkit-flex-flow: row wrap;
  justify-content: space-between;
  align-items: flex-end;
  height:1000px;
 
}

.flex-item {
  background: tomato;
  padding: 0px;
  width: 25%;
  height: 150px;
  border:1px solid #ccc;
  
  line-height: 150px;
  color: white;
  font-weight: bold;
  font-size: 3em;
  text-align: center;
  -webkit-box-sizing:border-box; -moz-box-sizing:border-box; box-sizing:border-box;
}
#pepito{
  height:300px;
  order:2;
}