Look up the meaning and category of an HTTP status code online, in your browser.
Enter an HTTP status code to get its standard name and category (Informational, Success, Redirection, Client Error or Server Error).
404 Not Found = the resource doesn't exist; 403 Forbidden = it exists but you are not allowed. The tool labels each code's category.
All the common standard codes from 100 to 504, including 418 I'm a teapot.