“超文本转移协议（HTTP）状态码注册表”放置在http://www.iana.org/assignments/http-status-codes，她已经被更新如下：

    1.    +-------+---------------------+-------------+
    2.    | Value | Description         | Reference   |
    3.    +-------+---------------------+-------------+
    4.    | 304   | Not Modified        | Section 4.1 |
    5.    | 412   | Precondition Failed | Section 4.2 |
    6.    +-------+---------------------+-------------+