Cookies: what are they, and what can they do?

Cookies enable a website to store a VERY small about of information on your hard drive, so that, when you return to that website, it can retrieve that information.

Online shopping stores use this facility..

eg: you can browse an online store, and place items in your "shopping basket" you can leave, and return, and the the website will "remember" the items you have picked.

Or..

a site like CNN custom news.

You can go to cnn.com and totally customize their page, eg: you are only interesting in aussie sports results, the weather, and entertainment news. Then, when you return to the custom news page, you only get the information you like.

A page might politely ask your name.. then every time you return, the site says "Welcome back, Fred"

A cookie CANNOT:
Send any other information to a remote site, other than what you specify (or type onscreen, in a form)

It can tell the remote website what Web Browser you use, and what version.

What OS (eg: windows3.1, or 95)
And a cookie can ONLY be "set" or "retrieved" by the website that created it.