Debit cards issued by Indian Banks can no longer be used on websites that do not support 3-D Secure. Registrations for 3D Secure(Verified by Visa, Mastercard Securecode) began on August 1st 2009, but cards were being processed properly by sites not supporting VbV/Securecode nonetheless. Starting December 2009 however, cards can only be used on sites supporting VbV/Securecode.
This doesn't bode well with users of websites like PayPal and Godaddy among others.
Credit Cards on the other hand continue to work as before.