If you go through the Home Page, on the right side there is a box with links to Amazon, EBay & LateRooms.com. Using these links to buy items gives a small return to the site which, as you point out, helps keep the site free (along with donations )
I never knew that!,what a bummer! I buy and have bought recently a load of stuff from Amazon.
I knew the adverts were there but I didn't know it helped the site.
Pity I'll remember in future as I buy a lot.