This problem started a few days ago. (Latest Firefox Update???) I log in to Outlook.com. The screen comes up normally with the Folders Pane on the Left, the E-mail Title Pane in the middle and the smaller Preview pane on the right of the screen. Normally I double click on the middle Title Pane and it selects and pops up to show the larger expanded e-mail. A few days ago the problem started that now when I double click on the middle Title Pane a message pops up "You May Now Close This Window". I can't get the e-mail to appear in the expanded middle pane. I switched to Chrome which is an alternate Browser that I use and I Did Not Have This Problem. Apparently the problem is caused by a change that Firefox made in the last few days. I have used Firefox as my default Browser for many years now and love this Browser. I have tried everything I could think of including allowing Popups for the Outlook.com website, and clearing the Firefox cache, but the problem still exists. Any help you can give me would be greatly appreciated. I do not want to have to use another Browser other than Firefox. I will be upgrading to Windows 10 from 7 in the next few weeks, but I'm not sure Windows 7 is the issue since Outlook.com works with no problems with Windows 7 using the Chrome Browser.