The following code shows how to nested row with fluid grid.
<!DOCTYPE html>
<html>
<head>
<script type='text/javascript'
src='http://code.jquery.com/jquery-1.8.3.js'></script>
<script type='text/javascript'
src="http://netdna.bootstrapcdn.com/twitter-bootstrap/2.2.2/js/bootstrap.min.js"></script>
<link rel="stylesheet" type="text/css"
href="http://netdna.bootstrapcdn.com/twitter-bootstrap/2.2.2/css/bootstrap-combined.min.css">
<style type='text/css'>
.span3 {<!-- w ww. ja v a 2s . co m-->
background-color: grey;
}
.span6 {
background-color: yellow;
}
.span9 {
background-color: blue;
}
</style>
</head>
<body>
<div class="container">
<div class="row-fluid">
<div class="span9">
<div class="row-fluid">
<div class="span6">nested col</div>
<div class="span6">nested col</div>
</div>
<!-- end nested row -->
</div>
<!-- end span 9 parent -->
<div class="span3">span 3</div>
</div>
<!-- end row -->
</div>
<!-- end container -->
</body>
</html>