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
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