You may notice if you use hotmail (not me, my wife) that you get warned every time you use it that you are not using Forefox, even though you are. And since hotmail "upgraded" then you now can not attach a file to a mail or sometime reply or make a new mail!
well, a fix.
in Firefox address bar type
then ok the message, look for "general.useragent.vendor" > right click on Ubuntu and Modify > then type Firefox in the box.
all should now be sweet