Certificate Service has not been working since couple of weeks. Hope that Chinese site gets fixed soon!! You can only avoid certificate errors by hacking your Nokia N8 either by using Dr Web hacking solution over here or by flashing it by following this guide.
S60 3rd Edition, S60 5th Edition and Symbian^3 Certificate Generator
You can now get a certificate for your Symbian Series 60 3rd edition, 5th edition and Symbian^3 handsets allowing you to sign your own applications and get rid of certificate errors.
1. Enter your IMEI in the box indicated. 2. Enter the verification code next to it. 3. Click on the submit button.
4. Return to this page after 24hrs and re enter your IMEI and verification code, you will be directed to a new page with 2 links. Click on the first link to download your new certificate.
How to download Cert n key file? Follow this Screen Shot
5. After, generating certificate and key file, grab POT Signing Tools by OPDA from: here 6. If POT Signing tool doesn’t work on your PC, try using Free Signer on your Mobile from here
7. You can also use SiS Signer by Jerome for signing unsigned apps, from here
Now Sign your applications and Install them without any Certificate Errors on your Symbian^3 Devices (Nokia N8, C7, E7, C6-01, X7 and E6).
Tired of Signing every single app with your cert and key? Its time to hack your phone with Dr Web Hacking Solution. Click here to learn more.