The following code shows how to set table header width with span6 span6.
<!DOCTYPE html>
<html>
<head>
<link
href="http://netdna.bootstrapcdn.com/twitter-bootstrap/2.2.1/css/bootstrap-combined.min.css"
rel="stylesheet">
</head><!-- www . j ava2s . c o m-->
<body style='margin:30px'>
<table class="table table-bordered table-condensed">
<thead>
<tr>
<th class="span6">span6</th>
<th class="span6">span6</th>
</tr>
</thead>
</table>
</body>
</html>
</body>
</html>