I recently got myself a brand new computer at work running the latest Visual Studio – Visual Studio 2015. After setting up a client’s EPiServer 10 environment I found everything working as expected; until I tried editing pages through EPiServer’s edit mode.
In FireFox (version 50.1.0) I got a top menu, the site preview as well as the left and right content panels; however, I was unable to edit any properties. Chrome (version 55) only gave me the top menu parts of the EPiServer edit mode, all else was blank.
As it turns out, I had Visual Studio 2015 installed with an extension called Web Accessibility Checker. This extension helps performing accessibility checks on ASP.NET web applications; like testing the DOM for compliance with standards such as WCAG levels A or AA.
After I disabled this extension in Visual Studio’s Tools menu, under the Extensions and Updates option, EPiServer’s edit mode started working again.
EDIT: Seems like Eric Herlitz encountered this problem as well back in September. Apparently it should be enough to disable the Browser Link; see Can’t load the EPiServer edit gui in development environment for more information.