Hi..
To change the target Frame work to 3.5 from 4.0 check the below figures you will get to know..
change the target Framework from ASP.NET 4.0 to ASP.NET 3.5.
1) Ensure IIS and the ASP.NET properties are configured for Framework 2.0. Note:
Framework 3.5 will not show up in the list of installed options due to
the fact that framework 3.5 is an extension of 2.0 and not a stand alone
release.
http://www.bnettechnologies.com/BnetBLog/image.axd?picture=ASP.NET%20Properties.png
2)
Configure you web application to use target Framework 4.0 by right
clicking your website in the solution explorer >> Property Pages
>> Build >> Change "Target Framework" to .NET Framework 3.5.
http://www.bnettechnologies.com/BnetBLog/image.axd?picture=VWD%20Site%20Properties.png
http://www.bnettechnologies.com/BnetBLog/image.axd?picture=VWD%20Build%20Properties.png
This will update your web.config file with the correct information.
hope this will help you..