Changing ASP.Net Version for your  Virtual Directory.

        Description: Virtual directories allow you to run multiple web applications on a single domain In virtual directories,

         the directory is accessed using the folder path instead of the subdomain name. A virtual directory in Plesk is a link to an

          existing physical directory that is present on the server's hard disk.

         Step 1: To change the ASP.Net version for your virtual directory, Login into the Plesk Control Panel then go for Websites & Domain

                     and then click on Virtual Directories.   

         Step 2: Under Virtual directory, tab click on ASP.net Setting.

        Step 3: Under Asp.net settings click on Change Version

        Step 4: Under Asp.net settings Select the ASP.NET VERSION and then click on ok and apply.