Why not use some brs?
<div class="mydiv-centerer">
<div class="mydiv">Some content</div><br />
<div class="mydiv">More content than before</div><br />
<div class="mydiv">Here is a lot of content that
I was not anticipating</div>
</div>
CSS
.mydiv-centerer{
text-align: center;
}
.mydiv{
background: none no-repeat scroll 0 0 rgba(1, 56, 110, 0.7);
border-radius: 10px 10px 10px 10px;
box-shadow: 0 0 5px #0099FF;
color: white;
margin: 10px auto;
padding: 10px;
text-align: justify;
display:inline-block;
}
Example: http://jsfiddle.net/YZV25/