You could certainly use notepad, just save your files .html, and you can preview them online. The only disadvantage is that you aren't really able to see when you make a semantic mistake, which becomes a pain when trying to fix problems - especially in HTML.
You may want to consider downloading or purchasing more advanced text-editing software. The more advanced ones will not only include syntax highlighting, but will also help you debug.
A good free program would be, for example, jEdit. If you're willing to spend money, many people use Adobe Dreamweaver, which is a great tool for new programmers. I'd also recommend you try using phpDesigner, which is a bit less expensive, and allows you to test more than just HTML - you can also test PHP and other languages if you decide to learn them.