Why Would You Want to Block Third-Party Cookies in Every Web Browser?
Most cookies exist for the sake of persistence. When you visit a website such as Facebook or Twitter, cookies let you stay logged until you log out again. This means that every time you visit that site, you will still be logged in, which saves you the time and effort of re-entering your password. If you clear you cookies, then you will be logged out (or rather, the browser will think you’re logged out because it will have no memory of you every visiting the site in the first place).
Third-party cookies are cookies placed on your device by a website other than the one you’re visiting. For example, say you visit a website and their advertiser(s) set a cookie–this allows that advertiser to track your visits to other websites. You probably don’t want this to happen.
You should also know that some websites might use third-party cookies that don’t constitute a privacy concern. Disabling these cookies might cause problems.
For example, you might try to view streaming video on a website, but the video originates from another source. In this case, you will likely see an error telling you that the video cannot be viewed. Often, the error message will provide little clue as to what the problem may be, but if you have third-party cookies disabled, that is most likely the culprit.
Finally, your browser may be able to block most third-party cookies, but not necessarily all of them.