Two examples: - From a working inspector, go to http://students.info.uaic.ro/~victor.porof/. This results in a blank markup view and the following error: Timestamp: 11/19/2012 05:41:18 PM Error: InvalidAccessError: A parameter or an operation is not supported by the underlying object Source File: resource:///modules/devtools/CssLogic.jsm Line: 1105 - From a workin inspector, go to a standalone image: -> blank markupview Original Github issue: https://github.com/joewalker/devtools-window/issues/261