Screenshot of the error?

It freezes the screen. yahoo mail freezes. note at top says "this is slowing down firefox browser. cliCk to STOP

Hey there! It sounds like you're facing an issue with Yahoo Mail causing Firefox to freeze. This can be frustrating, but let's get you back on track. It seems like an extension or add-on might be causing the problem. Try starting Firefox in Safe Mode by clicking on the menu (those three lines in the upper-right corner), then "Help," and "Restart with Add-ons Disabled." If Yahoo Mail works fine in Safe Mode, you can then identify the problematic extension and either disable or remove it. Additionally, clearing your cache and cookies might help. Go to the menu again, select "Options," then "Privacy & Security," and under Cookies and Site Data, click on "Clear Data." Remember to restart Firefox after doing these steps. Hopefully, this should resolve the freezing issue with Yahoo Mail.