It isn't possible at the moment to add a context= attribute to the <iframe> element that defines the browser's content area. This makes it hard to display a context menu when the user right-mouse clicks in the content area. I've discussed this with Dave and he indicated that he's got a plan.
Fixed. You will need to put the context="blah" on a box that wraps the iframe though. :(
Works as advertised. Minor problem: The context menu appears in the wrong position. The menu appears relative to the overall window rather than relative to the content area. Basically, it's off by the offset of the content area in the window. But I'll open another bug about that.