Customers unable to log-in to Santander's personal banking site this morning need to try another browser.
Several Reg readers got in touch with us this morning because they were met by a holding page which said: "We're sorry, but the online logon service for Online Banking is temporarily unavailable."
Customers were offered various phone numbers instead.
A spokesperson from Santander Cards said: "We are aware that some customers using the latest version of the browser Firefox, version 4, may currently be experiencing difficulties accessing their account details online. We are in the process of rectifying this and would advise customers in the meantime to use a previous version of Firefox or Internet Explorer.
"This will not impact customers' online security. Customers who are concerned can contact us by telephoning the number on the back of their card." ®