Web is originally and mostly an HTML world with page by page navigation. Oh yes there is flash but it is designed for graphist with massive website and it was always used for merchandising and promotion site.
In business, in the better case, we had some techno like Struts for it's Model View Controller architecture. Sadly this was not a good looking user interface with old fashioned page by page navigation with maybe some css styling.
It was at this time that GWT from Google appears. For me, it was amazing. Why ? firstly because it is like coding Swing (the desktop UI techno from Java) and it pushs the developper to see it's website like a desktop UI with frames, menus, buttons ... Secondly it was easy to code, easy to debug and easy to maintain.
Now GWT and similar techno have made their ways and it becomes better and better with more and more UI component like SmartGWT or Tatami Toolkit or AjaxSwing which converts your old Swing application to web with little (no ?) refactoring.