For example, LiveSearch can be carried out. This means that as you type keywords for a search, you see a list of results appear (without reloading the page). This is only one example; there are many applications for this type of web site design most of which are still to be invented.
Among the applications that use AJAX are Gmail, Windows Liveetc.
Today, only the more recent browsers can use AJAX (Internet Explorer versions 5 and higher, Mozilla Firefox, Google Chrome etc.).