Cookie data is name-value pairs stored on your hard-drive by a website. The website stores data on your computer and retrieves it when you return to the site to remember who you are. A website can only retrieve the data it has stored, and is not able to look at another cookie stored or other data on your computer.
The data moves in the following manner:
- When you type the URL of a website, your browser sends a request to the website for the page. For example, you type http://www.ebay.com to your browser and your browser then contacts Ebay's server and request its home page.
- When the browser does this, it will look on your computer for a cookie file that Ebay has set with a previous visit. If it finds a Ebay cookie file, your browser will send all of the name-value pairs in the file to Ebay's server.
- Ebay's server receives the cookie data and the request for a page. If name-value pairs are received, Ebay can use them to identify your interests with previous visits.
- If no name-value pairs are received, Ebay thinks that you are a new visitor. The server creates a new ID for you in Ebay's database and then sends name-value pairs to your computer. The process of storing name-value pairs on your computer begins again.
- The Web server can change name-value pairs or add new pairs whenever you visit the site and request a page.
You have control over this process. You can set an option in your browser so that the browser informs you every time a site sends name-value pairs to you. You can then accept or deny the values.