For an old DotNetNuke website I encountered the error:
Unable to find script library ‘/aspnet_client/system_web/1_1_1_4322/WebUIValidation.js’
I ran the command Aspnet_regiis.exe which is located in the directory C:\WINDOWS\Microsoft.NET\Framework\v1.1.4322.
C:\WINDOWS\Microsoft.NET\Framework\v1.1.4322/aspnet_regiis.exe -c
The utility aspnet_regiis.exe is installed a a part of the .Net Framework. Using the utility allows the version of .Net Framework to be registered with IIS once it has been installed.
For further information there’s Microsoft Technet’s details on aspnet_regiis.exe
