4. Delete browser cookies.
5. Contact the site directly. The admin of the site may not know about the 403 Forbidden error, please find contact information on the site to inform them about this error. Most websites have a technical support social network account, some even provide email addresses and phone numbers.
6. Contact your Internet service provider if you still get a 403 error while your friends still have access to the site. It is possible that your public IP address or ISP has been blacklisted, creating a 403 Forbidden error.
7. Visit the website at another time. When verifying the correct access page and everyone has the same error as you, visit the page after the error has been fixed.
The following messages are also client-side errors and involve 403 Forbidden errors: 400 Bad Request, 401 Unauthorized, 404 Not Found, and 408 Request Timeout. There are several HTTP status codes on the server side like 500 Internal Server Error and some other errors.
See also: How to fix 503 Service Unavailable errors