Question: I am having trouble finding a clear answer on this one. I have an ASP.NET 4.0 Silverlight app, but recently a ton of users are complaining about not being able to use the site on mobile devices and Linux distro's. The app is built on MVVM architecture, and thus we are considering changing the UI to alleviate the complaints. We are leaning toward HTML5, but I'm not sure if this is even technically possible with ASP.NET 4.0. I've seen some posts saying that HTML5 only works with javascript code behinds, and that with ASP.NET 4.5 HTML5 support will be added. Am I understanding this correctly? Maybe it would make more sense to just go with an ASPX UI, what are the advantages of HTML5 over .ASPX? Any help is appreciated.

Answer: 
HTML5 is a set of client-side technologies.  

ASP.Net is a server-side technology.  

They have nothing to do with each-other.

However, it will be easier in ASP.Net MVC.
I'm really surprised where somebody telling that all the C# code of the ViewModel and xaml code behind replace with Javascript . Is is possible ? Where in MVVM architecture code are huge and all are responsible for higher task(like communicate with service layer or database).
Is it possible to convert all C# code in JavaScript.

Even I have seen if a JavaScript function take over 25 lines than it becomes some clumsy fro developer to understand . Simple or small functionality can easy develop with javaScript .

C# is very standard and object oriented language ,to develop LOB it has great role but Javascript is not too much .

I'm think Using asp.net mvc is nice to use HTML5 , see we just need to change UI page look using HTML5 but rest of application functionality should remain Same .