The following code shows how to mark input group addon.
<!DOCTYPE html>
<html>
<head>
<link rel="stylesheet" type="text/css"
href="http://netdna.bootstrapcdn.com/bootstrap/3.0.0-rc1/css/bootstrap.min.css">
</head><!--from w w w. java 2 s .c o m-->
<body>
<div class="input-group">
<span class="input-group-addon">one word</span>
<input type="text" class="form-control" />
</div>
<div class="input-group margin_top_10">
<span class="input-group-addon">two word word</span>
<input type="text" class="form-control"/>
</div>
<div class="input-group margin_top_10">
<span class="input-group-addon">three word word word</span>
<input type="text" class="form-control"/>
</div>
</body>
</html>