Hey Marci - I've been leaving this for someone else to answer, mainly because I am not 100% certain of the correct answer to the Firefox issue, but seeing how nobody else has responded, I shall give it a shot:

With the Firefox issue: You will generally get a similar message to that if you are logged on to a site and perform some sort of search, order something, subscribe to something, register for something, etc...then navigate away from that page and then try to go back to it again. In other words; post information on a secure page, navigate away from that page and then try to go back to it again. The message you describe is not ecactly the same though. Could you post a screenshot of the exact message please?

With the multiple emails: There are several reasons why this might be happening. Most common cause is a setting within your email client. Which email client are you using (e.g. Outlook, Outlook Express, etc.)?
There is an option in the account settings to..."Leave a copy of message on server". This should be disabled. Open your email client and go to [b:2myitgd1]ToolsAccounts[/b:2myitgd1], highlight the account name and then click on the [b:2myitgd1]Properties[/b:2myitgd1] button. Click on the [b:2myitgd1]Advanced[/b:2myitgd1] tab and see if that option is enabled. If it is, just disable it, click on [b:2myitgd1]Apply [/b:2myitgd1]and then close out.

Please try that first and post back.

Cheers.....JIM