That is covered in the documentation links you have been given to read.
ladroge sent the following on 4/15/2008 6:30 AM:
> Someone can explain me the following error displayed when a customer want to
> valide an order on the merchant website?
>
>
http://www.nabble.com/file/p16700544/Sans%2Btitre.jpg
>
>
> Thanks