@Onager, @Tenacious,
To be technical: websites that (appear) to know what you looked at or searched for earlier, are collaborating.
When you search on Google/Amazon/whatever, this website stores information on that and/or share it with advertising companies.
Then when you visit some other site, the advertising company displays ads they think are relevant for you.
Not the key word here: collaboration.
Without collaborating, all a website can know is what you do on their website(s). They can't see what you did or do on other websites.
The only thing they can see is where you came from if you arrived by clicking a link (not if you type in the address yourself).
Now do you think JW are of the collaborating kind....?