Important Points :
- GWT provides Panels which can contain other panels and widgets. This is the basic mechanism by which GWT intends us to build user interfaces.
- GWT supplied panels and widgets run on all major browsers in a similar way.
- A RootPanel is the top-most panel to which all other widgets are ultimately attached.
- RootPanel.get() gets a singleton panel that wraps the HTML document's <body> element.
- Use RootPanel.get(String id) to get a panel for any other element on the page.
- eg. RootPanel rp = RootPanel.get() ;