Internet Information Services (IIS) 6 Resource Kit

HTTP Status Codes

HTTP status codes provide the best information about what is happening with IIS. On an active Web server, HTTP status codes provide a continuous feed of up-to-the-moment information about the activity and health of the server.

Most HTTP status codes have three digits, for example, 401. Some status codes have three digits followed by a decimal point, and one or two more digits (for example, 300.12). In such a case, the number that follows the decimal point is called the substatus code.

Codes within each hundred-number range provide specific types of information, as summarized in Table 18.2.

Table 18.2. HTTP Status Codes

Status Code Range	Type of Code
100	Informational
200	Successful
300	Redirection
400	Client Error
500	Server Error

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