Ajax Enhancements/Improvements in ASP.NET 4.0

Ajax is an acronym for Asynchronous JavaScript and XML. It is a combination of different technologies, used for building rich and responsive user interfaces. The benefits of using Ajax in your applications include:

• Faster page renderings and support for partial page updates
• Rich and, responsive user interfaces
• Reduced consumption of server resources

AJAX 4.0 provides some of the following features -

1. Support for Live data binding
2. Support for Client-side template rendering
3. Support for declarative instantiation of client components
4. Support for using the Observer pattern on JavaScript objects and arrays
5. Support for invoking ADO.NET Data Services and Data Contexts
6. Support for the DataView control

For More information visit below link

http://www.webreference.com/programming/asp/New-Features-AJAX4-0/