annoying blue bar at backend WYSIWYG editor

I found a blue bar in backend WYSIWYG editor no matter which articles or modules to edit.

blue bar 2.jpeg

May you tell me what goes wrong?

Regards,

Seth

Hi,

Thanks. However, it doesn't work. I changed the Editor Styles to default from template css, then the blue bar disappeared.

If you're using JCE is should work,
if still not you have to create a extra css for admin template which
body {background:white;}

tips are in JCE.