The container
class is intentionally not 100% width. It is different fixed widths depending on the width of the viewport.
If you want to work with the full width of the screen, use .container-fluid
:
Bootstrap 3:
<body>
<div class="container-fluid">
<div class="row">
<div class="col-lg-6"></div>
<div class="col-lg-6"></div>
</div>
<div class="row">
<div class="col-lg-8"></div>
<div class="col-lg-4"></div>
</div>
<div class="row">
<div class="col-lg-12"></div>
</div>
</div>
</body>
Bootstrap 2:
<body>
<div class="row">
<div class="span6"></div>
<div class="span6"></div>
</div>
<div class="row">
<div class="span8"></div>
<div class="span4"></div>
</div>
<div class="row">
<div class="span12"></div>
</div>
</body>