Comfortable typing HTML by hand, but want a little more functionality than you'd get in a basic text editor?
EditPad is a full-featured text editor that has been in development for a number of years; it originally was postcardware in the 1990s. (Postcardware means you were asked to send the programmers a postcard if you liked it). It works with Windows 98, ME, NT4, 2000, XP, Vista, and 7.
The software provides one tabbed window, which can contain any number of open files at once; attempting to run Editpad again when there's another instance running simply opens the new file in the same window.
One of the most useful things in the software in unlimited undo/redo functionality; as long as you didn't close the file, you can even undo changes after saving. This is particularly nice when you're testing different CSS options, as you can easily roll back a change if you don't like how the changed web page looks in your bowser.
The main disadvantage is that you have to upgrade to the paid version in order to get some of the most useful features. Most notably, only the pro version (which costs $50 for a license that lets you install it on any number of computers used by one person) has the syntax coloring, which makes programming in a number of languages (including HTML and CSS) much easier.