How to have a 100% width background inside container of twitter bootstrap?

[admin]

I am currently building a wordpress site, where I need a 100% width background (css color, no image) for a div. My div is inside a container and I can't modify the html. So, I was wondering if there was any way with css to do this. I have already tried the padding+margin hack, but it didn't work.

HTML:

<div class="container">
 <div class="row-fluid">
   <div class="main span12">
       <div class="row-fluid blue"> <!--this is the div that needs the background-->
          <div class="span4">some content</div>
           <div class="span4">some content</div>
          <div class="span4">some content</div>
          </div>
       <div class="row-fluid">
           <div class="span12"> some other content, doesn't need the background</div>
       </div>
     </div>
  </div>
  </div>

Any help is much appreciated. I tried this one : <a href="http://www.sitepoint.com/css-extend-full-width-bars/" rel="nofollow">http://www.sitepoint.com/css-extend-full-width-bars/</a> but it didn't work.