>Hi,
>
>My customers are using my ASP.NET application on their Intranets. The application runs on .NET 2.0 and is typically installed as site on their web server (usually Server 2008). I want to add some new modules as separate applications (that will have a different DLL) but I would prefer to start doing this in VS 2010 and use .NET 4.0. Therefore, on the same site I would have some .ASPX pages using DLL built in VS 2005 with for .NET 2.0 and other .ASPX pages using another DLL built in VS 2010 for .NET 4.0. Will there be a conflict? Anybody sees possible issue with this? TIA.

You can run applications under different versions of the .NET framework on IIS. In IIS, you can create different application pools and specify different .NET framework versions for them. To run an application under a specific framework, assign it to the application pool with that framework.