<div class="span12"></div> to force 100% width. By default every block has 100% width.
<div class="span6"></div>
<div class="span6"></div>
<div class="span4"></div>
<div class="span4"></div>
<div class="span4"></div>
<div class="span3"></div>
<div class="span3"></div>
<div class="span3"></div>
<div class="span3"></div>
<div class="span4"></div>
<div class="span8"></div>
<div class="span8"></div>
<div class="span4"></div>
<div class="span4"></div>
<div class="span4 offset4"></div>
<div class="span3 offset3"></div>
<div class="span3 offset3"></div>
<div class="span6 offset6"></div>
<div class="span6"></div>
<div class="span6"></div>
<div class="outer block span6">
<div class="outer block span6">
<div class="outer block span4">
<div class="outer block span4">
<div class="outer block span4">
<div class="outer block span4">
<div class="outer block span8">
<div class="outer block span8">
<div class="outer block span4">