StaffHi,
To address the tested objects in your test, you use the fully-qualified names which include the object name and the names of all of their parent objects. However, this approach is not reliable since the names of web elements can change between different test run sessions or even during the same session. The best way to address the tested objects is to use Name Mapping. This feature allows you to map web objects to custom (short and more readable) names and specify values that identify each of these objects on the web page. For more information, please read Name Mapping in the online documentation.
As for the FindChild method you are using, it returns the ambiguous window as you search for the objects whose WndClass property is MozillaWindowClass, but there are more than one of such objects. Try using another property for the search, for example, WndCaption.
