HTTP status codes

HTTP status codes are standard response codes given by web site servers on the Internet. HTTP status code is a Hypertext Transfer Protocol (HTTP) response status codes. This includes codes from IETF internet standards. The status code is part of the HTTP/1.1 standard (RFC 2616) and it has five classes.

1xx Informational (100 - 102):- indicates a provisional response
2xx Success (200 – 208 and 226):- indicates the action requested by the client was received
3xx Redirection (300 - 308):- indicates redirections
4xx Client Error (400 – 431 and 444, 449-51, 494-99): - indicates errors
5xx Server Error (500-511, 598 and 599):- indicates the server familiars

Note: - 5xx codes for the cases in which the server is aware that the server has erred. However, the 4xx codes are intended for cases in which the client seems to have erred.

503 Service Unavailable:-

The 503 Service Unavailable errors can appear in any browser in any operating system. The 503 Service Unavailable error is a server-side error, meaning the problem is usually with the web site's server. It is possible that your computer is having some kind of problem that is causing the 503 error but it is not likely.

504 Gateway Timeout:-

The 504 Gateway Timeout error is occurred when one server did not receive a timely response from another server that it was accessing while attempting to load the web page or fill another request by the browser. The 502 Bad Gateway is also similar to this error.

403 Forbidden Errors:-

The 403 Forbidden errors is an HTTP status code that means that accessing the page or resource you were trying to reach is absolutely forbidden for some reason. In other words, “Go away and don't come back here."

By far the most common reason for this error is that directory browsing is forbidden for the Web site. Most Web sites want you to navigate using the URLs in the Web pages for that site. They do not often allow you to browse the file directory structure of the site. For example try the following URL (then hit the 'Back' button in your browser to return to this page):

This URL should fail with a 403 error saying "Forbidden: You don't have permission to access /accounts/grpb/B1394343/ on this server". This is because our CheckUpDown Web site deliberately does not want you to browse directories - you have to navigate from one specific Web page to another using the hyperlinks in those Web pages. This is true for most Web sites on the Internet - their Web server has "Allow directory browsing" set OFF.

Robot.txt file is responsible for these type error. HTTP Error 401 Unauthorized is also similar problem.