bootstrap的输入框与bootstrap组件会错位解决方法

<div class="col-sm-8 "> <div class="input-group"> <span class="input-group-addon glyphicon glyphicon-user "></span> <input type="email" class="form-control " id="inputEmail3" placeholder="用户名"> </div> </div>

一直错位，然后：

<div class="input-group"> <span class="input-group-addon glyphicon glyphicon-user "></span> <input type="email" class="form-control glyphicon glyphicon-user" id="inputEmail3" placeholder="用户名"> </div>

glyphicon glyphicon-user添加了这个就对齐了