Why XML file is not rendered properly in Firefox?

for me, It turns out that some sort of Skype add-on was the problem. Great detective work. It's odd how that click-to-call extension creates such random issues...

just disable skype click-to-call add-on, after that Firefox showing row xml

In my case, XML page was displaying blank and when I View Page Source (option available when you right click on the page or by pressing Ctrl+U), the complete XML is there.

It was solved when I disabled Awesome Screenshot add-on.

I suggest that you try deactivating add-ons one-by-one!

I had the same issue and I found out that the Evernote webclipper add-on was messing up my firefox. Once I disable it I was able to view a pre-formated xml.