Can you show what that means? What happens on this site? --> https://www.irs.gov/downloads/irs-pdf It works for me. see screenshot Did you try with Firefox in Troubleshoot Mode? https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode#w_how-to-start-firefox-in-4troubleshoot-modesf5safe-modesf What OS? I'll guess Windows... If windows, home or pro? Are you running any security software besides MS Defender?