500 Internal Server Error
This is the most common error that web users will see. It is a general-purpose error, and can occur any time a web server encounters an internal problem. Error 500 happens most often when a web server is overloaded.
Web users will likely stumble across this error after a failed login attempt. Basically, it means the user tried to access a site they didn’t have access to.
400 Bad Request
This error message will appear when something has gone wrong with your web browser. It means that your request was corrupted in some way.
When there is no login opportunity on a page, you will get a 403 error on a page if you try to access a forbidden directory on a website.
404 Not Found
When a user tries to access a web page that doesn’t exist, they will get a 404 error. This is usually the result of a broken link, a web page that has been moved, the user mistyped the URL, or the page was simply deleted.
408 Request Timeout
A 408 error occurs when the user stops the request before the server finished retrieving information. This error will appear when a user closes the browser, clicks on a link too soon, or hits the stop button. It is also common to see this error when a server is running slow, or a file is very large.
501 Not Implemented
When this error appears, it means the user has requested a feature that the browser does not support.
502 Service Temporarily Overloaded
A 502 error occurs when there is server congestion. Usually this error corrects itself, when web traffic decreases.
503 Service Unavailable
If the site is busy, or the server is down, users may get a 503 error.
Connection Refused by Host
This error is very similar to the 403 error. It means the user either doesn’t have permission to access the site, or an entered password is not correct.
File Contains No Data
When a page is there, but nothing shows up, users can see a file contains no data error. This error is probably caused by stripped header information or bad table formatting.
Cannot Add Form Submission Result to Bookmark List
Only a document or a web address can be saved as a bookmark. If a user tries to save any other type of form, they will get this error.
Helper Application Not Found
If a user tries to download a file that requires the use of a helper program, this particular error may appear, if the browser cannot find the required program.
TCP Error Encountered While Sending Request to Server
When this error occurs something has gone wrong on the line between the requested site and the user. Sometimes this is hardware related, so all instances of this error should be reported to a network administrator.
Failed DNS Look-Up
A failed DNS look-up error means the web site’s URL could not be translated. Due to overload, this error is most common on commercial sites. The best thing to do when this occurs is to try again later.