this is one of the "it depends" answers.
The thing with .Net is that if you have an IDE (Visual Studio), you can develop not only ASP.Net pages, but you can also use form applications, WPF, Silverlight, services, etc. Whatever it is, a programming language for use in .Net (C #, VB.Net).
I would suggest setting priorities in what you want to focus on. Some ASP.Net noobs I've worked with have been focusing too much on the HTML / GUI side, while there is nothing wrong with learning, they tend to compromise OOP core skills. You need to understand why you use ASP.Net compared to a static HTML page — you want your web pages to become “dynamic.” To achieve this, you need to do internal programming, not just markup and javascript. Forget the drag-n-drop objects mentioned in the tutorials, if you work in a corporate / professional environment, you are unlikely to be able to use them.
I started learning HTML when I was 15 (I’m 27 now) and these years of experience made my HTML and Javascript code trivial tasks, and I was able to focus more on C # logic.
The problem, although starting up as a Windows Forms programmer, they usually had to learn websites with difficulty. Some do not understand the page life cycle concepts and limited states offered by ASP.Net. If they use ASP.Net Forms, they almost automatically abuse ViewState objects to achieve what they want, and abuse ASP.Net AJAX control.
Try to find a balance between these two scenarios, and you'll be fine. Good luck