Most of the website design and editing I do, I do by hand using a text editor such as vim or notepad even but occassionally, especially if I am trying to lay out tables, CSS, or image maps (I hardly ever mess with image maps but sometimes) HTML Kit is an excellent tool to help with these tasks.

HTML Kit Screenshot

HTML Kit allows you to preview the output of your code as you edit. It is also very useful in planning site layout. There are a ton of plugins available for HTML Kit to automate just about any coding tasks.

The built in validation tools are also nice. (Probably should use them more often).

From the authors site:
HTML-Kit is a full-featured editor designed to help HTML, XHTML and XML authors to edit, format, lookup help, validate, preview and publish web pages. Despite its name and the light download size, HTML-Kit is a multi-purpose tool that has support for several scripting and programming languages.

Again if you are looking for a great FREE web development tool download HTML Kit and give it a try: http://www.chami.com/html-kit/