49. The method of claim 1 , further comprising: for mixed type documents, displaying a root document, and custom UI widgets to represent a sub-document.
49. The method of claim 1 , further comprising: for mixed type documents, displaying a root document, and custom UI widgets to represent a sub-document. 50. The method of claim 49 , wherein the custom UI widget to represent a sub-document comprises a button which contains a thumbnail image associated with the sub-document.