Why are credit card details necessary?

The hotel requires your credit card details to guarantee your reservation ONLY. Your card will NOT be charged until your arrival. At this stage you may be asked to pay by cash or with an alternative credit card accepted by the hotel, this is your choice.
Usually the payment is on your check-out. Some hotels will require you to produce a method of payment upon arrival - whether it is cash, bankers cheque or credit card.

If you fail to cancel your reservation and do not arrive at the hotel, the hotel may charge your credit card with a cancellation fee - usualy equal to the cost of the first nights accommodation (written on confirmation you have recieved).

Most hotels accept all major credit cards, however, there are exceptions. You can see on each hotel page a list of the credit cards that are accepted by the hotel.