In .NET 4.0, the ClickOnce deployment technology is enhanced with the following features:

Support for .NET Framework 4.0 version - CREATES applications by using Visual Studio 2010 that can target .NET Framework 4.0 and its new features.
Support for multiple versions of the .NET Framework - Creates applications that are compatible with multiple versions of the .NET Framework. You can SPECIFY the target framework for an application as .NET Framework 3.5 or .NET Framework 4 while creating the application.
Enhanced logging feature - Stores logging information that includes various parameters passed to the ClickOnce runtime, the browser settings, and ClickOnce SECURITY options.
Custom INSTALLER and User Interface - Allows you to create a custom GRAPHICAL user interface for installing and updating the .exe applications. In addition, the custom installer can have custom dialog boxes for security and maintenance operations.

In .NET 4.0, the ClickOnce deployment technology is enhanced with the following features:

Support for .NET Framework 4.0 version - Creates applications by using Visual Studio 2010 that can target .NET Framework 4.0 and its new features.
Support for multiple versions of the .NET Framework - Creates applications that are compatible with multiple versions of the .NET Framework. You can specify the target framework for an application as .NET Framework 3.5 or .NET Framework 4 while creating the application.
Enhanced logging feature - Stores logging information that includes various parameters passed to the ClickOnce runtime, the browser settings, and ClickOnce security options.
Custom Installer and User Interface - Allows you to create a custom graphical user interface for installing and updating the .exe applications. In addition, the custom installer can have custom dialog boxes for security and maintenance operations.