It looks like your website is missing a reference to the Infragistics2.WebUI.Shared.v8.3 assembly, or that it's expecting a version of this assembly (8.3.20083.1009) that's different than the one you have. Add a reference to this version of this assembly to your project.
In general, this reference should be added automatically. You might also want to consider re-running the Toolbox Utility to ensure that your Visual Studio Toolbox tabs refer the same version of the NetAdvantage assemblies that you have installed.
i got the same errors while using Ultrawebmenu and all other infragistic components
how can I add the missing reference to the Infragistics2.WebUI.Shared.v8.3 assembly??
In the same way you'd manually add a reference to any other assembly. The following article from our online help files for NetAdvantage for .NET 2008 Volume 3 provide additional information, including links to relevant MSDN articles:Adding an Assembly to a Project