If you are already familiar with .NET, you might find some courses on Microsoft Virtual Academy a good starting point. There is a web development category: https://mva.microsoft.com/training-topics/web-development#!i...

Looking at the courses available, I would probably start with: https://mva.microsoft.com/en-US/training-courses/getting-sta...

then look into either ASP.NET MVC: https://mva.microsoft.com/en-US/training-courses/introductio...

or ASP.NET Core: https://mva.microsoft.com/en-US/training-courses/intermediat...

This is coming from someone that hasn't actually used these, so take my recommendations with a grain of salt.