here you go: this is the fiddle Demo
<div class="row-fluid">
<div class="span4">
<div class="well">1<br/><br/><br/><br/><br/></div>
<div class="well">5</div>
</div>
<div class="span8">
<div class="span12"><div class="well">2</div></div>
<div class="row-fluid">
<div class="span8">
<div class="well">3</div>
<div class="well">6</div>
</div>
<div class="span4"><div class="well">4<br/><br/><br/><br/><br/></div></div>
</div>
</div>
</div>
<div class="row-fluid">
<div class="span2">
<div class="well">7<br/><br/><br/><br/><br/></div>
<div class="well">14<br/><br/><br/><br/><br/></div>
</div>
<div class="span10">
<div class="row-fluid">
<div class="span6">
<div class="well">8</div>
</div>
<div class="span6">
<div class="well">9</div>
</div>
</div>
<div class="row-fluid">
<div class="span3">
<div class="well">
10<br/><br/><br/><br/><br/>
</div>
</div>
<div class="span6">
<div class="well">11</div>
<div class="well">12</div>
</div>
<div class="span3">
<div class="well">
13<br/><br/><br/><br/><br/>
</div>
</div>
</div>
<div class="row-fluid">
<div class="span6">
<div class="well">15</div>
</div>
<div class="span6">
<div class="well">16</div>
</div>
</div>
</div>
</div>
you are not completely free on the panel sizes using span, if you want a more precise result you should use custom percentages on the div width.