Try this on Safari...
From your Safari menu bar click Safari > Preferences then select the Security tab.
Deselect: Allow all other plug ins
Quit and relaunch Safari. Try Facebook. If that made a difference, follow the instructions for trouble shooting third party plugins here.
If it's not a plug in issue, select the Extensions tab in the Safari > Preferences pane.
If there are any installed, turn that off, quit and relaunch Safari to test.
If nothing above has helped, please post a Safari crash report in your reply.
If Safari has just crashed, press the Report button on the CrashReporter dialog box to view the crash information.
Now *copy/paste the entire contents* of the Crash Reporter window into your reply here. If the crash report dialog does not appear or the crash is hard to reproduce, crash logs can be retrieved from the ~/Library/Logs/CrashReporter> folder.