error_page 500 /custom_500.html;
error_page 502 /custom_502.html;
error_page 503 /custom_503.html;
error_page 504 /custom_504.html;
error_page 404 /custom_404.html;
error_page 401 /custom_401.html;
error_page 403 /custom_403.html;
error_page 405 /custom_405.html;
error_page 400 /custom_400.html;
error_page 417 /custom_417.html;
error_page 421 /custom_421.html;
error_page 429 /custom_429.html;
error_page 497 =444 /error.html;

error_page 402 501 505 506 /error.html;

location ~ /custom_(4[0123459][0-9]|5[01][0-9])\.html {
    root ${NGX_HTML_DIR};
    internal;
}

location ~ /error.html {
    root ${NGX_HTML_DIR};
    internal;
}