How cookies work

Let's say you go to a website and it has a quiz with question one on the first page and question two on the second etc.

When you go to the second page, the web server needs some way of knowing that you are the same person who answered 'A' for example on page one.

That way, when it comes to adding up your score it can combine all your answers, from many different pages, all together.

Putting a cookie on your computer allows the server to remember that you are the person with that unique cookie and it can recognise you wherever you go on that site even though you aren't logged in.

If the computer didn't give you a cookie it wouldn't know whether it was the same person visiting all the pages.

It's because of things like this that some websites even refuse to let you in if you don't accept cookies - so you could be missing out.

Third party cookies

Third party cookies are the ones that have got users concerned about their privacy most worried.

In theory, only the website which placed a cookie on your computer can see that cookie so it shouldn't be possible for any other sites to look at that cookie.

When a cookie is placed on your computer, it records the name of the website that will be allowed to reopen it in the future.

If 'Super Supermarket' places a cookie in its name then only 'Super Supermarket' should be able to open it.

The problem is that many sites use cookies from other third parties like marketing companies and give them permission to look at the cookie.

By doing this marketing companies can track you across all the sites that use their cookies.

They do this to get an idea of your viewing and shopping habits and then share that information with the websites who are their customers.