Ajax client-side framework failed to load Asp.Net 4.0

Question

I got a complicated problem with ASP.Net 4.0 Ajax....I started a website with Visual Studio 2010 on my machine,and added some update panels they used to work fine,but sudden

Answer 1

1. If .Net Framework 4.0 client Profile is not available in your machine , so repair .net Frame work 4.0 or re install .
2. go to Project Property and select target framework 3.5.