Previously, hotels were restricted via their General Delivery Terms with the online travel agency on bidding on certain keywords, such as "booking.com" and other trademarked terms on Google AdWords and generic search terms.

In a letter sent to hoteliers last week, Booking.com says: "We removed the bidding restrictions from our agreement with you. This means you're free to bid on Booking.com via online search engines if you want, which aligns with a recent EU (European Union) ruling.