What Cookies Can and Can't Do
Because cookies involve writing to and reading from your visitors' hard drives, cookie-friendly browsers deal with lots of security issues. As a result, using cookies has many limitations. The most important ones for the purposes of this chapter are these:
Not everyone has a cookie-friendly browser.
Not everyone who has a cookie-friendly browser chooses to accept cookies (but most people do).
Each domain may have only 20 cookies (so use them sparingly).
There is a 4KB limit on the amount of information one domain can store using cookies. That's just over 4,000 characters—actually quite a lot.
A website can set and read only its own cookies (for example, Yahoo! can't read AOL's cookies).
Keep these limitations in mind when ...
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