Whether you surf the Internet sporadically or you hardly ever leave Reddit, you have likely run across the occasional HTTP status code. Perhaps your favorite website displayed a 400 error, or maybe you saw a 502 error when exploring older, lesser-known sites.

But what exactly do these status codes mean?

Test your knowledge with the following questionnaire to discover the difference between each code.

1. What Is HTTP ERROR 101 – Switching Protocols?

A. It’s a beginning college class explaining how to switch diplomatic documents

B. It’s a page that requires you to switch from one browser to another

C. It indicates that the server is changing to a different version of HTTP

Answer: C

HTTP, Hypertext Transfer Protocol, is the method by which you communicate with someone else’s server. When you click a link or submit a form, your browser sends a request to the server for information. When the server receives that request, it sends back an HTTP response with information for you.

In the case of a 101 error, you sent a request to the server to change the application protocol used in your connection. The server accepted your request, then tried to comply via the Upgrade message header field. Once it switches protocols, the 101 error should disappear.

2. What Happens with a 204 No Content Error?

A. You deleted all your content

B. The server processed your request but won’t return any content

C. You forgot to fill out a required form

Answer: B

When a 204 error occurs, you request information from the server, but the server has no new information to send back.

For example, if you have an HTML form and submit it, and the server returns a 204 status code, the browser will not refresh the form or take you to another page. Your view of the document does not change, and all the data you entered remains the same.  

Usually you won’t ever see the 204 status code. From your browser, it will look as though nothing has happened.

3. Oh No! Your Favorite Website Has a 301 Error! What Does This Mean?

A. It means that your favorite site has crashed and you must restart

B. It means the site has moved to a new URL

C. It means the owner of the site hasn’t updated the page in years

Answer: B

URLs change for a variety of reasons. Perhaps the webmaster decided to purchase a URL that readers can remember. Or maybe he or she corrected a spelling mistake in the original URL. Whatever the case, the content you know and love has moved to a new address.

A 301 error lets search engines know that the old page no longer exists at that URL and to pass credit on to the new page. Sometimes 301 pages automatically redirect you to the new page without requiring any action from you. Other times you simply have to click the new link.

4. You See a 400 “Bad Request”—What Did You Do?

A. You typed in the wrong URL or clicked a link with a mistake in it

B. You did something naughty and the server didn’t like it

C. You clicked a few too many times which interrupted your original request to the server

Answer: A

Although 400 errors happen for multiple reasons, they most common occur because of a mistake in the URL. Perhaps you wanted to go to examplesite.com/file.html but you accidentally typed examplesite.com/fiel.html, or you clicked on a link with a similar mistake. Essentially you requested a page from a site that the server doesn’t understand.

However, 400 errors also happen when you have an old, corrupt cached copy of the page you’re trying to view, or your browser has a few too many old cookies. In these cases, you’ll want to clear your browser’s cookies as well as its cache to fix the problem.

5. “502. That’s an error.” What Error?

A. The server exceeded its bandwidth

B. The server is temporarily down

C. Your firewall prevents you from accessing the page

Answer: All of the Above

This was a bit of a trick question, as 502 errors cover a lot of possible problems. Most of the issues tend to fall on the server side, so you can’t do much to fix them.

For example, you might see Twitter’s famous “fail whale” error indicating Twitter is over capacity. When this happens, you can try refreshing or restarting your browser or accessing the site at another time.

If these techniques do not work, the problem could result from a conflict with your firewall. To protect your computer from malicious attacks, your firewall might keep you from communicating with the web server. You may need to adjust your firewall rules to access the site.

See an Error Not Listed Here?

These are just a few of the basic HTTP status codes that your computer might face on a regular basis. For a full list of status codes, click here.

If you’re not sure why you see any of these status codes while surfing the internet, you may need to contact your IT technician to help you pinpoint the problem.