Recent email exploits and complaints have changed web email (not your machine) to be more secure. Gone are the days for some web email where you only needed to log in and it would remember you.
As you didn't reveal which web email I can only write that a REMEMBER ME check box exists on Yahoo mail which keeps you logged in if you don't have some cookie cleaner enabled.
Bob
I have a Vista Home Premium, 32 bit, IE 8 browser. I close my last browser and have to log back in to get my email. Why? Any help will be much appreciated. At one time i did not have this problem. Tnanks ahead of time.

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