Script Summary: Deletes any site's cookies whenever you want. It doesn't block cookies so it allows for logins, shopping baskets, etc., but clears the cookies when you close its tab (customizable). Mark the site for auto-cookie deletion from the Grease Monkey submenu option, "User Script Commands." The script also adds a small transparent icon at bottom left, initially if there are cookies set by the site it shows them briefly (or the icon can be disabled). Cookies set by other sites through html frames are also shown, if no referrer is sent by the browser then all frames are checked.
Version: Cookie Zapper
If a site has not been set by the user for auto cookie deletion then the icon shows only if cookies are set. To delete these cookies, right-click on the icon. Right click again to see the results.
The background color of the zapper icon at bottom left of page changes colour depending on the setting for that site: beige when cookies are to be deleted on Tab close, blue when they are to be deleted when a page from that site/domain is unloaded (browsed away from), red when cookies are to be deleted when the site is visited, and white when not set at all.
If "Zap Cookies by default" is enabled, anytime a site's cookies are manually deleted via right click on icon or GM menu, this is learnt, so that this site's cookies will get automatically deleted in future. This is so unless the manual option for that site was explicitly set, the manual option is #4 under menu dialogue of the GM menu option "Cookie Zapper, Setup [toggle]..."
Session cookies are short lived and go away once the browser is restarted. It is only possible to manage those cookies that last longer. Session cookies are completely ignored by this script. So if you see cookies being displayed at the bottom left by this script these are all long term cookies and unless you delete them they will remain with you for a long time.