That is the new Outlook interface that MS uses instead of Hotmail.
If you want to return to Hotmail then click the gear shaped Option button to see a return to Hotmail item.
Hotmail shows an Upgrade to Outlook in its options menu.

Thank you. I did finally stumble on the 'gear' icon, and ended my frustration. Looking pretty is not an option to functionality.

Yahoo... you did it!! I'm home again, thanks soooo much!

You can no longer disable or uninstall Microsoft Outlook on Firefox according to their website. They are discontinuing firefox email and migrating to Outlook.