The following code shows how to create Large input group.
<!DOCTYPE html>
<html>
<head>
<script type='text/javascript'
src='http://code.jquery.com/jquery-git2.js'></script>
<link rel="stylesheet" type="text/css"
href="http://getbootstrap.com/assets/css/docs.css">
<link rel="stylesheet" type="text/css"
href="http://getbootstrap.com/dist/css/bootstrap.css">
<script type='text/javascript'
src="http://getbootstrap.com/dist/js/bootstrap.js"></script>
</head><!--from w ww . j a v a 2 s . c om-->
<body style='margin:30px'>
<h3 id="btn-groups-single">Large input group</h3>
<div class="input-group">
<span class="input-group-addon input-lg">@</span> <input type="text"
class="form-control input-lg" placeholder="Username">
</div>
</body>
</html>