The text in yahoo today and msn today when I launched them? It has changed to plain text why?

This only started after I started using Firefox internet browser and the first time i launched internet explorer after using Firefox for a few days? The text changed to plain text (like a printable page) It was ok in firefox before I launched then it chanched in both? So now when launch either browser they are in plain text? I think this is easy to solve but its got me foxed! Any ideas???