Generally you don’t have to pay for your room in advance when booking online. You are only required to register your credit card to guarantee your reservation.
There are however special offers available for selected time periods which have different payment conditions. Those clearly noted offers do require advance payment.
You can choose from the following online payment methods: VISA, MASTERCARD, AMEX, PayPal, Klarna Sofort Banking (instant bank transfer), giropay (if you have a German bank account which is registered for giropay) as well as PostFinance (if you have a Swiss bank account with PostFinance).