Nice Valentine's Day gift from HotelTravel.com – get $50 for bookings made on HotelTravel.com
Use code LOVEHTN.
Minimum booking value required is $150.
Not valid for "pay at hotel" bookings.
Update: It seems it only works for 2 night stays and you will need to switch to German before being able to apply the coupon.
Update II: Just made a booking The email confirmation will show the full amount (before applying the voucher) but the correct amount was authorized on my CC.