You really can't, and there's no easy way to selectively trust some. For example, one time I went through the huge list of certificate providers in Firefox and

You really can't, and there's no easy way to selectively trust some. For example, one time I went through the huge list of certificate providers in Firefox and manually disabled a bunch of countries and only left in a few major providers I heard the name of before. My day to day browsing worked just fine, with no noticeable impact, but it was not something I can manage on a regular and just a one-off experiment.