<div class="opacity-demo"><p style="color: rgba(0,0,0,1)">Opacity of 1</p>
<p style="color: rgba(0,0,0,0.75)">Opacity of 0.75</p>
<p style="color: rgba(0,0,0,0.5)">Opacity of 0.5</p>
<p style="color: rgba(0,0,0,0.25)">Opacity of 0.25</p>
<p style="color: rgba(0,0,0,0)">Opacity of 0</p>
</div>

In style element (<style type="text/css">) within head element:

.opacity-demo {
  background-image: url('images/satin.png');
  color: white;
}
.opacity-demo p { font-size: 200%; font-weight: bold; font-family: helvetica,sans-serif;}