How to check if Microsoft .NET is installed using Javascript
This script checks if the navigator.userAgent return string contains "NET CLR".
If that is found it checks for the specific version of the Microsoft dotnet framework.
This provides an easy and fast help for your users.
If the framework is missing, the user can be either directed towards the download sites at Microsoft or led to an installer including the .NET framework.
If the framework is already in place, the visitor enjoys a smaller download.