The site is?

If you use a proxy or VPN then try to use a direct connection. You can try to clear the Cache and remove the Cookies for websites that cause problems via the padlock button or via "3-bar" Firefox menu button (Options/Preferences) to see if that fixes it. I've also seen cases where having "Resist Fingerprinting" enabled caused this issue to occur. *https://support.mozilla.org/en-US/kb/firefox-protection-against-fingerprinting If this all doesn't work then you can try "Forget About This Site" in the right-click context menu of an history item. ---- You can remove all data stored in Firefox for a specific domain via "Forget About This Site" in the right-click context menu of an history entry ("History -> Show All History" or "View -> Sidebar -> History"). Using "Forget About This Site" will remove all data stored in Firefox for this domain like history and cookies and passwords and exceptions and cache, so be cautious. If you have a password or other data for that domain that you do not want to lose then make sure to backup this data or make a note. You can't recover from this 'forget' unless you have a backup of involved files. If you revisit a 'forgotten' website then data for that website will be saved once again. *https://support.mozilla.org/en-US/kb/delete-browsing-search-download-history-firefox