Pretty solid way to center vertically with HTML/CSS. From http://css-tricks.com/centering-in-the-unknown/

SemanticBlockElementsToCenterVertially.css

.something-semantic {
   display: table;
   width: 100%;
}
.something-else-semantic {
   display: table-cell;
   text-align: center;
   vertical-align: middle;
}

SemanticBlockElementsToCenterVertially.html

<div class="something-semantic">
   <div class="something-else-semantic">
       Unknown stuff to be centered.
   </div>
</div>

UnknownElementToCenterAgainst.css

/* This parent can be any width and height */
.block {
  text-align: center;
}
 
/* The ghost, nudged to maintain perfect centering */
.block:before {
  content: '';
  display: inline-block;
  height: 100%;
  vertical-align: middle;
  margin-right: -0.25em; /* Adjusts for spacing */
}

/* The element to be centered, can
   also be of any width and height */ 
.centered {
  display: inline-block;
  vertical-align: middle;
  width: 300px;
}

UnknownElementToCenterAgainst.html

<div class="block" style="height: 300px;">
    
    <div class="centered">
        <h1>Some text</h1>
        <p>But he stole up to us again, and suddenly clapping his hand on my shoulder, said&mdash;"Did ye see anything looking like men going towards that ship a while ago?"</p>
    </div>
    
</div>