Contrary to the other comment, of course it helps to disable third-party cookies. There are some other ways to identify users, e.g. the E-Tag header or canvas-

Contrary to the other comment, of course it helps to disable third-party cookies. There are some other ways to identify users, e.g. the E-Tag header or canvas-based methods. But cookies are the main and most reliable tool. You can go one step further and just always use Incognito/Private mode for sites that don't require a login. If you need to be logged in a lot, Firefox Account Containers are a new feature to separate site data.