HTTP (Hypertext Transfer Protocol) is a method in which we (or more appropriately, our computers) communicate with servers, and vice versa. There are essentially two parts to all web actions: a request and a response. For example, whenever we click a link, our browser sends a request to a server for information. When the server receives that request, it sends back a response.
This usually happens seamlessly, and we as requesters get an expected response. Again, and very simplistically, we click a link (request), and the server on the other end brings us the web page we want (response). But what happens when we don't get what we're expecting? Sometimes we're taken to another page or site than we were expecting. Sometimes we see an error message with a code number. What do these mean? Below is a list of some common HTTP status and error codes and what they mean.
Here's a comprehensive list: https://en.wikipedia.org/wiki/List_of_HTTP_status_codes
200's - Success
Typically, any status code beginning with a 2 is successful. It means the request was received and processed by the server.
300's - Redirects
Status codes beginning with a 3 indicate the destination has moved, with 301 being the most common of the 300 status codes. A 301 is a Permanent Redirect. It means the web page the user requested has been permanently moved to a new location. The response received from the server should include the new location, and it alerts the client (your browser) to use the new location the next time it tries to go to the same page.
A redirect is commonly set up when a domain (URL) is changed. Rather than force users to type in a new URL for a website or page they may already be familiar with, the server will automatically redirect them to the correct new location of the page.
400's - Page Not Found
You've ended up at a link that is either an invalid link, or where content has been moved or deleted. If you believe the link should be valid, or if you've changed your URL and are still getting traffic to the old link, contact TRIBUS so that a redirect can be setup.
500's - Server Error
Contact TRIBUS if you encounter this error.