Most involved having access to the machine that the person was using, or the network they were on. This has changed that. There are may issues surrounding this, privacy being the most obvious. Visit some of the links below to get further information. Microsoft's page explains some of the points I have mentioned, as well as how to disable and read cookies that are on your browser.
Cookies offer many opportunities for webmasters to refine, improve, and customize their sites.
When motivated by the visitors best interests, they are a powerful tool. When exploited unethically they can be dangerous. Cookie Central - information on persistent cookies, HTTP cookies, cookies with JavaScript, magic cookies, the dark side of cookies. Cookie Pages, The - full guide to http cookies JavaScript cookies. Lots of info cookies for homepages.