According to W3Counter, what percentage of browsers used Firefox?
CREATE TABLE "usage_share_of_desktop_browsers_for_june" (
  "source" text,
  "chrome" text,
  "internet_explorer" text,
  "firefox" text,
  "safari" text,
  "opera" text,
  "other" text
);
SELECT "firefox" FROM "usage_share_of_desktop_browsers_for_june" WHERE "source"='w3counter';