Another user has the same problem.

https://support.mozilla.org/kb/Clear+Recent+History#w_how-do-i-remove-a-single-website-from-my-history

Remove History For One Site

Open the History Manager <Control><Shift> H. In the search bar, enter the name of the site. Right-click on one of the listings and select Forget About This Site. This should remove all information, including any passwords / settings.

Dear FredMcD, Thank you for the help, it has worked. This also fixed my facebook issue where the chat disappears.

Kind Regards, Momo (Momoster69)

Glad to help. Safe Surfing.

i have same problem in another site but i not have the "forget about this site" option ...any other solution ?

Lanselot said

i not have the "forget about this site" option

Why not?

Start Firefox in Safe Mode {web link} by holding down the <Shift> (Mac=Options) key, and then starting Firefox.

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

yes and i have only flash player extension so i doubt depend on that ( i know safe mode only disable extension ) already cleared cache and cookie too is 3 days i couldn't load a site and i notice the same site load with google translate but with a very basic graphics...here my topic https://support.mozilla.org/en-US/questions/1194910 hope someone have solution for this...fortunatelly isn't an important site but still wanna be able to load it...

Lanselot said

i have same problem in another site but i not have the "forget about this site" option ...any other solution ?

turns out it was a spoofer agent plugin/addon i was using that was causing all these problems, the deleting history bit only worked due to the fact that I restarted the browser thus refreshing the spoofer agent and changed my agent info (browser info, os details and etc). So are you using any?

everything is default and 3 days ago same site worked i made no changes after , im using incognito mode so nothing get saved but still li deleted cookie - cache don't know what to do anymore , i have recently made a refresh too maybe i should do it again ... also if i prefer not...

For those still having a problem, a post was flagged as Solved Problem. so others that can help may not read this post.

Please go to the top of any support.mozilla.org web page and use the Ask A Question link; https://support.mozilla.org/en-US/questions/new Select the product for what the problem is (Firefox or whatever).

Now select the category for the problem. At the bottom is Other.

Describe the problem in brief. Then press <enter>. The website will display any prior posts that might help you. If nothing on the list can help, at the bottom press the button; None Of These Solve My Problem.

Now enter all the relative information on the problem. At the bottom of this, you can Add Images.

Under this is Troubleshooting Information. Please press the Share Data button. This will let us look at your system details. No Personal Information Is Collected.

i have alredy post a topic https://support.mozilla.org/en-US/questions/1194910