What Are Cookies?
Cookies are small files which are stored on a user's computer. They are designed to hold a modest amount of data specific to a particular client and website, and can be accessed either by the web server or the client computer. This allows the server to deliver a page tailored to a particular user, or the page itself can contain some script which is aware of the data in the cookie and so is able to carry information from one visit to the website (or related site) to the next.
Each cookie is effectively a small lookup table containing pairs of (key, data) values - for example (firstname, John) (lastname, Smith). Once the cookie has been read by the code on the server or client computer, the data can be retrieved and used to customize the web page appropriately. This is how some sites "remember" you from a previous visit, and save your login information if you've asked the site to do so. This is also why if you clear your computers' cookies and revisit a site that's previously saved your login, you'll have to re-enter your login information again.
How Long Do Cookies Last?
Cookies, by default, last as long as your current browsing session and are destroyed when you close your browser. However the creator of the cookie can set the expiry date far in the future, often years in the future.
How Do I Know If I Have Cookies Enabled?
You can visit this Cookie Checker page and it will tell you.
Enabling Cookies
For most browsers, cookie settings are under the "Privacy" settings tab (typically "Tools -> Options -> Privacy", or on Apple products look for "Settings" or "Preferences", and the "Privacy" or "Accept Cookies button or tab from there.
Some browsers give you a choice between accepting "1st-Party Cookies" and "3rd-Party Cookies". "1st-Party" would be a cookie from the site you're on, such as ours. "3rd-Party" would be a site linked or somehow included in the site you're visiting, such as when we link to PayPal from our site or in an email. Another example would be if a site you visit allows commenting through a Facebook plugin or Disqus. Sadly 3rd-party cookies can also be used for tracking and/or advertising purposes, which is why they are falling out of favor.
Many browsers have 3rd-party cookies disabled by default: Safari, IE6, IE9 (if you use in Protected Mode), IE10 and (starting with version 22) Firefox.
Cookie Acceptance Options
You don't have to accept all cookies from all websites, but keep in mind that many services and actions on the web rely on the use of cookies to complete or save information between website visits. You can enable all cookies or only for certain sites that you trust.
Deleting Cookies
You can always delete any and all cookies after they've served their purpose, and in fact conventional wisdom in the web privacy community is that users clear their cookies every few months. There are a lot of good software options for clearing out junk files (including cookies), and the one we recommend is CCleaner. CCleaner will let you choose which cookies you want to keep, and though it's easier and quicker to delete them all, there will likely be cookies you want to keep, to save yourself from having to login each time, etc.
The other side of that is that occasionally a website will change it's login procedure or page, and change the cookie that's set. Having a stale cookie by the same name can cause issues; it's rare but it does happen. The act of logging out of a website or service is supposed to cause the AUTH (login) cookie to be destroyed, but some sites, some BIG sites, don't expire the cookies properly.
If you want to delete cookies manually, you can normally do that in the same settings area in your browser where you enabled cookies, or by deleting your browsing history.
