Is this only happening on Facebook?
Safari/Preferences/Advanced - enable the Develop menu, then go there and Empty Caches. Quit/reopen Safari and test.
Then try Safari/History/Show History and delete all history items showing that web site address by control - clicking on the entry, the select delete.
Go to Safari Preferences/Extensions and turn all extensions off. Test. If okay, turn the extensions on one by one until you figure out what extension is causing the problem.
Go to Finder and select your user/home folder. With that Finder window as the front window, either select Finder/View/Show View options or go command - J. When the View options opens, check ’Show Library Folder’. That should make your user library folder visible in your user/home folder. Select Library/Caches/com.apple.Safari/Cache.db and move it to the trash.
If that doesn't work, try running this program in your normal account , then copy and paste the output in a reply. The program was created by etresoft, a frequent contributor. Please use copy and paste as screen shots can be hard to read. On the screen with Options, please open Options and check the bottom 2 boxes before running. Click “Share Report” button in the toolbar, select “Copy Report” and then paste into a reply. This will show what is running on your computer. No personal information is shown.
Etrecheck – System Information