Hi,
As in the screen shot below, you can see there is an underline for CE. If we hover over that, then we get unrecognized tag prefix or device filter CE.
We have this at the top of the page, so I am not sure why it is not able to recognize CE -
As for the stylesheet issue, we are not seeing any errors. It just doesn't seem to pick up styles from our external stylesheet inspite of adding EditorWysiwygModeCss.
Thanks,
Priyanka