There is security software like Avast and Kaspersky and BitDefender and ESET that intercept secure connections and send their own certificate. http://www.ehow.com/how_11385212_troubleshoot-reset-connection-firefox.html https://support.mozilla.org/en-US/kb/server-not-found-connection-problem https://support.mozilla.org/en-US/kb/firefox-cant-load-websites-other-browsers-can https://support.mozilla.org/en-US/kb/secure-connection-failed-error-message https://support.mozilla.org/en-US/kb/connection-untrusted-error-message '''http://kb.mozillazine.org/Error_loading_websites''' '''This Connection is Untrusted''' is sometimes caused because the computer system clock is wrong. Check the time / date / time zone settings. ------------- Separate Issue; Your System Details shows; Installed Plug-ins Shockwave Flash 20.0 r0 Shockwave Flash 17.0 r0 Shockwave Flash 14.0 r0 <br>Having more than one version of a program may cause issues. You must remove the older programs. Then get the current full installer. Flash: Grab the uninstaller from here: '''[http://helpx.adobe.com/flash-player/kb/uninstall-flash-player-windows.html Uninstall Flash Player | Windows]''' '''[http://helpx.adobe.com/flash-player/kb/uninstall-flash-player-mac-os.html Uninstall Flash Player | Mac]''' Then reinstall the latest version. Flash Player '''Version 20.0.0.286<br>https://www.adobe.com/products/flashplayer/distribution3.html''' '''Note: Windows users''' should download the ‘’’active_x’’’ for “Internet Explorer,” '''and''' the ‘’’plugin’’’ for “Plugin-based browsers” (like Firefox). Note: Windows 8 and Windows 10 have built in flash players and Adobe will cause a conflict. Install the ’’’plugin’’’ only. Not the ’’’active_x’’’. Adobe still offers Flash 18.0.0.326 as its extended support release further down

When I check https://www.duelingnetwork.com/ Firefox raises two problems: (1) the certificate is for https://host.duelingnetwork.com/ and not the www site, and (2) the certificate is self-signed, meaning that no trusted certificate authority is vouching for the server being the real one. I don't think Firefox has changed how it evaluates these kinds of certificate flaws, so I can think of three possibilities: (A) The site broke the server (B) Someone else hacked the server or hijacked this address (C) You were using it on an HTTP address http://www.duelingnetwork.com/ so Firefox didn't raise these issues before When I try to go to their forum our security service tells me it is unsafe, so something might be wrong on this site.