Error 500 (Internal Server Error) usually points to a script/plugin issue or incorrect file permissions — check your error logs in cPanel. Error 403 (Forbidden) means you don't have permission to access a page, often due to missing index files or permission settings. Error 404 (Not Found) means the specific page/file doesn't exist at that URL — check for typos or moved/deleted content. If your site is fully down, first check whether your hosting/domain has expired before assuming it's a technical fault — expiry is the most common cause we see.