Why doesn't this work?

[Helmut]

This is maddening.

I'm expecting a bordered box the full width of the page with the word 
"texleftt" on the left and the word "textright" 1/2 of the way over.  

Instead, nothing is in the box and the words are stacked on each other.

<div class="container"> 
  <div class="row">
    <div class="masthead"> 
<div class="span4">
textleft
</div> 
<div class="span8">
textright
</div> 
    </div>
  </div> 
<div><!--container-->

CSS:

.masthead {
border:thin solid #CCC; 
}