HTML files are just text files with a fancy name. Therefore, you can use any text editor around to edit them, even notepad. I've been developing web pages for a long time, and I use only Notepad++ for my work. It colors the syntax correctly for almost ANY language. It's free to download from the link below.
There are, what they call, WYSIWYG (What You See Is What You Get) editors, like Dreamweaver or FrontPage (now called Expression). Although these are not free, there are many free ones out there that can work just as well.
If you are more into the designing of web pages, like the graphics and such, I would recommend a WYSIWYG editor. If you like to code, Notepad++ may suffice. G'luck!