How Can I Stay Logged on to Facebook with Safari?

Recently I have had a lot of trouble with Safari....I get the spinning ball frequently, it is slow, etc. One thing it is doing consistently is not allowing me to stay logged on to Facebook. I have to log in every single time even if I am just off 2 or 3 minutes. At first I thought it was Facebook, but it is not. I have no trouble with my iPad....stay logged on forever. On my iMac, I have no trouble with Firefox. It is only Safari where this problem is occuring. I have checked all the preferences, and permissions with Disc Utility. I don't know what else to do to get Safari working smoothly. I used to be able to dump the preference file and that usually helped, but now there doesn't seem to be any preference file (Lion). I have also reset Safari several times. Any suggestions?