Visual Studio.NET is a Microsoft IDE for developing both desktop and web applications. It offers developers a choice of languages to work in and allows those languages to work together. I too am currently working at web design company as a developer and found it very diverse and interesting. For example, an ASP.NET web application has elements of HTML and ASP in it. For behind the scenes coding or data retrieval will be functions written in VB.net, C#.net or both. And suppose you have a running countdown clock on the page...that's likely a Javascript function. So I've listed 5 different languages all working together on one website.
For your purposes, I'd look into C#.net. It will be an extension of what you already know from your C++ and JAVA work.