There is a various error that happens on the web page. Some of them are listed below:
1) 400 - Bad Request
The 400 bad request error is an HTTP status code that user send as a request to the server, which is very simple to load a web page but sometime it might be incorrect or corrupted that server doesn't understand it.
2) 401 - Authentication Required
In this type of error, a page needs a user name and password to access it. In case, you try to access it without password and user name then you get a 401 - Authentication Required message.
3) 403 - Forbidden
You will come across forbidden errors when any user tries to access a directory, file, or script without appropriate permissions.