New version of the most famous front-end framework Boostrap released just few hours ago. You will find many improovements such as:

• Official sass port
• Dropdowns now have their own alignment classes
• Form feedback styles for validation states now include optional icons to reinforce color changes

Also new examples, new docks plus improved build tools.

Get it from here: http://getbootstrap.com/getting-started/#download

Or use the cdn:

<!-- Latest compiled and minified CSS -->
<link rel="stylesheet" href="//netdna.bootstrapcdn.com/bootstrap/3.1.0/css/bootstrap.min.css">

<!-- Optional theme -->
<link rel="stylesheet" href="//netdna.bootstrapcdn.com/bootstrap/3.1.0/css/bootstrap-theme.min.css">

<!-- Latest compiled and minified JavaScript -->
<script src="//netdna.bootstrapcdn.com/bootstrap/3.1.0/js/bootstrap.min.js"></script>