HTML/XHTML Editors
Since HTML/XHTML is just plain text, there are many different editors you can use to edit your Web pages
Programmer's Code Editors
Many code editors are available and most work fine for editing your HTML/XHTML, although they may have many features that are not relevant for Web pages. A good general free programmer's code editor is Komodo Edit, which runs of Windows, Mac, and Linux and checks your HTML/XHTML as you enter it.
HTML/XHTML Editors
HTML/XHTML editors are specifically for working on Web pages. Most offer ways to place the tags for you, which reduces errors. A nice free HTML/XHTML editor is HTML-Kit. It runs on Windows and includes the Tidy utility.
Web Site Management Programs
A Web site management program like DreamWeaver gives you a huge toolset for managing all the files in a Web site.