Since many sites offer buying of items and services online
and to help them some sites provides their services to help the customer.but while making an account on such sites like paypal ,alertpay and others they ask to add ur credit card information. But people who think adding your card is not safe to these sites,by the way this is fully safe,but still you you dont want to add your card to these sites then try making virtual credit card,this is the service offered by banks for online things.I dont know about other banks but HDFC provides this service and I also registered on Paypal using this.
Once you register on HDFC bank for netsafe you get a functionality to create a virtual card.opt that and create your card.This card is same as your card with different card number.its expiry period is around 3 months( I guess) and once its used it gonna expire.SO its the safest thing you can do.Try HDFC bank for this service and enjoy the services of paypal with much more comfort...!!!
If you have any more query regarding this ask me...I'll let you know all about this...!!!!