Assembly Problem

Question

Could not load file or assembly 'System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified.

wat is "System.Web.Extensions"? I tried to Add reference but its not there(Add Reference table).
Wat it means Plz sumone explain it properly, How to over come this error

Niradhip Chakraborty · Answer

you can installed System.Web.Extensions.dll into the Global Assembly Cache (GAC) otherwise they won't have enough privilege to run some parts of themselves correctly. The element creates a configuration section and subsections for the SystemWebExtensionsSectionGroup class. You set the properties for these sections in the element. The element provides elements that can be uncommented to configure how Web services are called from Microsoft ASP.NET AJAX applications. The element is used to specify custom type converters and to override default settings for JSON serialization. The element specifies custom type converters. The element is used to enable or disable the authentication service. The element is used to enable or disable the profile service and to specify which properties are exposed by the service. The element is used to enable or disable caching and compression of resources used with scripts. The element element and element can be defined only in the Machine.config file or in the Web.config file in the application root directory. The element can be defined in the Machine.config file in the Web.config file in the application root directory or in a Web.config file in a subfolder of the Web site. The following example shows the element for ASP.NET AJAX. Add this section and its subsections to the existing Web.config file as a child of the element. custom converter --> type=Acme.SubAcme.ConvertMeTypeConverter/> --> Include requireSSL=true if appropriate. --> --> allow profile properties to be retrieved and modified in ASP.NET AJAX applications you need to add each property name to the readAccessProperties and writeAccessProperties attributes. --> readAccessProperties=propertyname1propertyname2 writeAccessProperties=propertyname1propertyname2 /> --> enableCaching=true /> -->