Center DIV content Fluid Vertical and Horizontal

This is the example I have:

Line height does not apply to fluid divs. The code I have is currently based on line-height but the the sizes of the boxes change. So how can I have a link (content) always in the exact middle?

I want to make sure that the content inside this DIV is always going to be equally centered from the top and the sides. Vertical and Horizontal centered.

Current code: (note style tag is blank as this is dynamic filled)

    <style type="text/css">
    .box{
    width:468px; /* php changes this sometimes */
    height:60px; /* php changes this sometimes */
    background:#eee;
    text-align:
    center;
    border:
    1px solid rgb(177, 172, 171);
    line-height: 61px;
    }
    </style>

    <div style="" class="box" id="">
<a style="color:#333;font-weight:bold" href="claimPrize();">Winner!</a>
</div>

Ran into a similar situation not too long ago, did a search and found an article about absolute centering from css-tricks, here is the article and an accompanying fiddle to test it out.

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;
}

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>

<div class="block" style="height: 200px;">

    <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>

<div class="block" style="height: 600px;">

    <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>

Demo

http://jsfiddle.net/andresilich/YqKMH/