This error was received when attempting to edit a content editor web part (CEWP):
Error: ‘style.display’ is null or not an object
When he moved the web part to a lower part of the page (for example) he received another pop-up error:
When he attempted to move the web part to another zone I receive the generic SharePoint error page saying: “”An unexpected error has occurred.”” … and it will not move the web part to another zone.
This error occurs when more than one web parts gets referenced with the same id.
According to blogs out on the Internet, this usually happens when content is copied into a content editor web part from either another web part or a Microsoft Office application.
Naturally users need to be encouraged to remove inline styles when copying content.
To fix the problem, I had to delete the faulty web part and re-create it.
Without being able to get in through the edit menu, I broke into the page and deleted the faulty web part, by adding ‘?contents=1’ to the end of my url.
This is a little trick that forces SharePoint to redirect you to the spcontent page.
From here you can use this page to close Web Parts on your page, restore defaults to Web Parts, or delete Web Parts from your page.