Bootstrap表单控件可以具有与输入一起流动的块级帮助文本。要添加全宽内容块，请在<input>之后使用.help-block。
以下示例说明了这一点
<!DOCTYPE html> <html> <head> <title>Bootstrap Example</title> <link href = "/bootstrap/css/bootstrap.min.css" rel = "stylesheet"> <script src = "/scripts/jquery.min.js"></script> <script src = "/bootstrap/js/bootstrap.min.js"></script> </head> <body> <form role = "form"> <span>Example of Help Text</span> <input class = "form-control" type = "text" placeholder = ""> <span class = "help-block"> A longer block of help text that breaks onto a new line and may extend beyond one line. </span> </form> </body> </html>