Visual development has been a standard process for many professional web application development team. Since 1995, techniques and tools have been developed and been improved.
We're in the process of taking the basic building blocks to the next level. Ajax style features will certainly be the part of the mix.
1. Ajax: A New Approach to Web Applications
Take a look at Google Suggest. Watch the way the suggested terms update as you type, almost instantly. Now look at Google Maps. Zoom in. Use your cursor to grab the map and scroll around a bit. Again, everything happens almost instantly, with no waiting for pages to reload.