Why did the aspnet_client folder come back in ASP.NET 4?

I recently upgraded my MVC 1 project (ASP.NET 3.5) to MVC 2 (ASP.NET 4). I noticed there is now a folder "aspnet_client\system_web\4_0_30319" under the site root. This folder is empty... I'm just wondering if anyone knows why it was created.

I remember the aspnet_client folder from the days of .NET 1.1, but I thought it was obsoleted when .NET 2.0 came out. For example, see the answers in these two stackoverflow posts:

What is the aspnet_client folder in my ASP.NET website?

What is the aspnet_client folder fo开发者_如何学编程r under the IIS structure?

So I'm just curious why it's back.

According to the self-paced training guide for exam 70-562 (ASP.NET with version 3.5 of the .NET Framework) written by Mike Snell and company, and published by Microsoft, one use for this folder (at least up to version 3.5, or runtime 2.0.50727) is for global themes (a theme for all sites in your domain). In this section they describe creating a themes directory under aspnet_client like so:

[iisdefaultroot]\Aspnet_client\System_web\[version]\Themes

where iisdefaultroot is C:\inetpub\wwwroot and version is 2.0.50727 for example.

Within the Themes folder, create a subfolder with your theme name, and apply it as you would with any other theme.

They note that

...Visual Studio does not recognize the global theme name in the IDE; however, ASP.NET processes it properly when you retrieve the page in the browser.

I personally haven't tried this, but thought I'd throw it out there.

From my experience, it is still obsolete, and, just like your first link, got created with the (new) aspnet_regiis procedure. Personally, I've found that I could just delete it and the sites continued to work fine, though I've only done one or two Asp.NET 4 sites.

Really obnoxious, IMHO.