Help for HyperText Transfer Protocol (HTTP) errors
Web browsers, such as Internet Explorer and Firefox use HTTP to access objects (e.g. web pages and images) on web servers. Whenever the server responds to a browser, it returns a 3 digit numeric status code and a textual “reason phrase”. The status codes are standardized, whereas the reason phrases can vary between servers. The first digit indicates the class of the code (e.g. client or server error), and the remaining digits identify the particular status.
| Class | Code | Reason1 |
|---|---|---|
| 4xx Client error | 400 | Bad Request |
| 401 | Unauthorized | |
| 403 | Forbidden | |
| 404 | Not Found | |
| 405 | Method Not Allowed | |
| 5xx Server error | 500 | Internal Server Error |
| 501 | Not Implemented | |
| 502 | Bad Gateway | |
| 503 | Service Unavailable | |
| 504 | Gateway Timeout | |
| 505 | HTTP Version not supported |
Several products report HTTP errors with their own description:
- Adobe Flash Media Server
- Apache status codes and messages
- Microsoft IIS web servers provide extended numeric status codes.
HTTP headers
You can view them with online tools such as web-sniffer.netExtra information
For information about- HTTP versions and specifications, see HTTP 505: HTTP Version Not Supported
- The types of methods for HTTP access, see HTTP 405: Method Not Allowed
- The format of HTTP requests, see HTTP 400: Bad Request
- The format of addresses (URLs) used to identify web objects
If you're curious about what weird and interesting stuff can appear in HTTP headers, see:
A. Wooster: “Fun With HTTP Headers”