Relative or absolute URL that points to a certificate renewal form.
According to documentation:
«It is a relative or absolute URL that points to a certificate renewal form. The renewal form will be accessed with an HTTP GET method using a url that is the concatenation of renewal-url and certificate-serial-number. Where the certificate-serial-number is encoded as a string of ascii hexadecimal digits. For example, if the netscape-base-url is https://www.certs-r-us.com/, the netscape-cert-renewal-url is cgi-bin/check-renew.cgi?, and the certificate serial number is 173420, the resulting URL would be: https://www.certs-r-us.com/cgi-bin/check-renew.cgi?02a56c The document returned should be an HTML form that will allow the user to request a renewal of their certificate»