I want to buy bitcoin through my bank debit or credit card. So which site is the best and secure to buy bitcoin through debit or credit card.
Depends, where do you live?
The best sites are usually those that use your local currency. If you live in the US it's easy because most exchanges accept USD and but if you are located somewhere in India or Korea, you're best using a local exchange.
The deal is simple. You have Euro in your pocket, find an exchange that accepts Euro transfers.