Is it possible to create a website with HTML and C # without ASP.NET?

Yes, HTML is standard. CSS is also almost mandatory in practice. JS will probably be used. All this on the client side.

On the server side you can use virtually any language. C # is one of them, and the most viable. It is one of the 3 languages most used throughout the web.

You do not need to use classic ASP.NET, but you may want to use some other technology next to it . You can use technologies other than ASP.NET, you can take these technologies that are open source and modify it to suit your needs. An example is Nancy quoted by Omni.

If you want you can reinvent the wheel, but even though I like it for more control, I probably would not.

Detail how to do is very broad, but the two main ways is to use the web server API, probably IIS or Apache, sending messages to him of what he wants to provide and receive his messages from requests or use CGI , there basically is write on the console and configure for the server to capture this. Each server can have its own way of communicating with the server application.

You need to find a good reason to do this. If it's performance I think there are other better ways to reach the goal. If you do not have to learn a technology, it probably does not make up for the effort you have to make in the hand.

Note that it is possible to avoid WebForms that is obsolete and considered bad by many, or even avoid MVC which is a bit heavy, improved in ASP.NET Core, but is still a cannon to kill bird in many cases. You have problems that do not need models and drivers. And it's true that in the simplest cases, the last thing you'll want to do is communicate with the HTTP server at hand. For this there is Razor Pages .

It's good to remember that ASP.NET Core has HTTP server itself , which can be used in many situations , but not all.

You have questions on the site in more detail.