The Server Response Codes

100-199	SRCs provide confirmation that a request was received and is being processed. (silent)
100	This is good. The request was completed and the process can move along.
101	Request to switch protocols (like from HTTP to FTP) was accepted.
200-299	SRCs report that requests were performed successfully. (silent)
200	It simply means all is OK. What the client requested is available
201	This means a new address was successfully created through a CGI or posting form data.
202	The client's request was accepted, although not yet acted upon.
203	The accepted information in the entity header is not from the original server, but from a third party.
204	There is no content in the requested click. Let's say you click on an image map section not attached to a page. This allows the server to just sit there waiting for another click rather than throwing an error.
205	This allows the server to reset the content returned by a CGI.
206	Only partial content is being returned for some reason.
300-399	Request was not performed, a redirection is occurring.(usually silent)
300	The requested address refers to more than one entity. Depending on how the server is configured, you get an error or a choice of which page you want.
301	Page has been moved permanently, and the new URL is available. You should be sent there by the server.
302	Page has been moved temporarily, and the new URL is available. You should be sent there by the server.
303	This is a "see other" SRC. Data is somewhere else and the GET method is used to retrieve it.
304	This is a "Not Modified" SRC. If the header in the request asks "If Modified Since", this will return how long it's been since the page was updated.
305	This tells the server the requested document must be accessed by using the proxy in the Location header (i.e. ftp, http.)
400-499	Request is incomplete for some reason.
400	There is a syntax error in the request. It is denied.
401	The header in your request did not contain the correct authorization codes. You don't get to see what you requested.
402	Payment is required. Don't worry about this one. It's not in use yet.
403	You are forbidden to see the document you requested. It can also mean that the server doesn't have the ability to show you what you want to see.
404	Document not found. The page you want is not on the server nor has it ever been on the server. Most likely you have misspelled the title or used an incorrect capitalization pattern in the URL.
405	The method you are using to access the file is not allowed.
406	The page you are requesting exists but you cannot see it because your own system doesn't understand the format the page is configured for.
407	The request must be authorized before it can take place.
408	The request timed out. For some reason the server took too much time processing your request. Net congestion is the most likely reason.
409	Conflict. Too many people wanted the same file at the same time. It glutted the server. Try again.
410	The page use to be there, but now it's gone.
411	Your request is missing a Content-Length header.
412	The page you requested has some sort of pre-condition set up. That means that If something is a certain way, you can have the page. If you get a 412, that condition was not met. Oops.
413	Too big. What you requested is just too big to process.
414	The URL you entered is too long. Really. Too long.
415	The page is an unsupported media type, like a proprietary file made specifically for a certain program..
500-599	Errors have occurred in the server itself.
501	What you requested of the server cannot be done by the server. Stop doing that you!
502	Your server has received errors from the server you are trying to reach. This is better known as the "Bad Gateway" error.
503	The format or service you are requesting is temporarily unavailable.
504	The gateway as timed out. This is a lot like the 408 error except the time-out occurred specifically at the gateway of the server.
505	The HTTP protocol you are asking for is not supported.