When the user tries to save internal error pages, they have the option of saving them as "complete XHTML" or as "file only". If the page is saved as complete, then the contents of the error page itself are stored on disk; if the page is saved as file only, the browser tries to fetch the page again from the server. Maybe, the "Save As" behavior when an error page is displayed could be similar to the one triggered by a reload, with the difference that errors would be conveyed through the Download Manager. Since we don't have a "real" document at hand, we may also want to disallow saving an error page as complete. Another possibility (but I don't like it very much) is to disable the "Save As" command completely for error pages, however we should still handle the case where an error page is currently displayed in a subframe. This change would probably require a separate UI review. Note that these considerations do not apply to error pages generated on the server (with HTTP failure status codes). The user might want to save the contents of these pages anyway; see bug 145124.