When using Safari, on some sites (ie/ facebook) it will not accept my password, it just keeps coming back to the log in screen.

I purchased a second hand ibook G4 for my son and mother to use for light internet surfing. On some sites (ie/ facebook, heroup.com) when we enter correct log in info for our accounts it will not accept, it just keeps coming back to the log in screen. I've tested this by logging in with the same info on our Acer laptop and all is well, no problems. What makes this really interesting is that on other sites (ie/ Apple, Yahoo) I am able to log in without a problem.

Does anyone have ideas for me to try to work this out?

thank you 🙂