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Creating Web Apps  «Prev  Next»
Lesson 4 What exactly are cookies?
Objective Describe the characteristics of cookies.

Cookies Defined

Cookies are identity tags stored on a user's computer. They provide a way for a Web site to keep track of a user's online behavior pattern. In general, cookies share these characteristics:
  1. They are never greater than 4 KB in size.
  2. They have a standard structure.
  3. They each have designated expiration dates and times.
  4. They are unencrypted.
  5. They store user preferences.

Why use cookies?

Cookies are used to work around the HTTP protocol, in which the server retains no information about the state of a connection with a visitor, it simply drops that information. While that poses no problem for most Web activity, it is undesirable for transaction-based activities such as shopping online. For example, a user may fill a shopping cart one day and may want to come back another day to complete the transaction. Cookies help retain the state of transactions over time.
You will learn more about how cookies work in the following SlideShow.



Web Cookie Process

User options

Preferences for accepting or rejecting cookies are set in the browser. Although the name of the options change from browser to browser; in general, users can set the following preferences:
  1. Do not allow cookies.
  2. Allow cookies.
  3. Ask each time.

Implications

Developers have no control over the preference settings in browsers of visitors. The implication is that site functionality could disappear if a site relies on the use of cookies and the visitor does not accept cookies. Developers must choose between providing two versions of the site: one for those who accept or allow cookies and one for those who do not. The alternative is to design one site and risk losing visitors.
In the next lesson, you will learn how cookies are created.

On Your Own

Click the link below to practice testing the effects of cookies on a Web site.
Testing Web Cookies