How it works...

In this recipe, we tested both application pools framework versions. Each application pool can be used for one or several websites.

We can check what happens if our application pool is v3.5 and we host a web application made for v4.0:

We get an error here. At the bottom of page, you can see the suggestion, which is Version Information: Microsoft .Net Framework Version 2.0.50727.8745; ASP.NET Version 2.0.50727.8745 and your web application framework is v4.5.

You must make sure to upload the supported .NET web application version and check the application pool associated with the website. Both should be the same framework version in order for the web page to run.