Overview of Mozilla embedding APIs
contract-id: ns_webbrowser_contractid implemented interfaces: nsiwebbrowser nsiwebnavigation nsiwebbrowsersetup nsiwebbrowserpersist nsiwebbrowserfind nsiwebbrowserprint nsiwebbrowserfocus nsibasewindow requestor interfaces: nsidomwindow nsidomdocument nsiwebprogress nsiclipboardcommands nsiprompt related interfaces: nsiprompt nsiwebbrowserchrome nsiwebbrowsersitewindow nsiwebprogresslistener nsicontextmenulistener nsiprintoptions overview: most of gecko's functionality...
...being reviewed interface definition: nsiwebbrowser.idl nsiwebbrowsersetup this interface is used to enable or disable various capabilities of a nswebbrowser instance.
...being reviewed interface definition: nsiwebbrowsersetup.idl nsiwebbrowserchrome this interface provides access to the window containing an nswebbrowser instance.

nsIWebNavigationInfo
you may specify null to check for compatibility with nsiwebnavigation objects that are in their default state; otherwise, the result is determined based on the configuration of the specified object (that is, how it is configured by using nsiwebbrowsersetup).