Online Code Editors & IDEs for Web Development
Nowadays, there are some quite sophisticated code editors that can be used in a browser. They have a similar design and functionality to local code editors. You don't need to install anything, so you could even use them on a foreign computer, e.g. in a library. But you might need to register a user account before you can use one of them.
These code editors allow you to create multiple files, just like you can in a local editor. The filenames are listed on the left in a sidebar. These files are kind of virtual, meaning they are not saved on your computer while working in the online editor. Nonetheless you should be able to create a website with multiple pages and link from one page to another (e.g. Home, Contact, About, Imprint...) in such editors. The ones I have used also have an option to download all the files of your project so that you can continue developing on your computer with a locally installed code editor.
Here is a list of popular candidates:
On a related side note, Shawn Wang noticed that online editors are becoming more and more popular because they have some advantages when working in a team with multiple developers (e.g. switching quickly between different code versions, everything runs on Linux and is preconfigured, etc.).
When creating your first project, you need to select something like "web project", "HTML", or "vanilla JavaScript". Or you create an empty project and create a new HTML file. Some details about creating and saving a file as HTML and adding HTML code are mentioned on the next page: Your First HTML Page