Mozilla Suite Composer is an open-source HTML editor that "keeps getting better with dynamic image and table resizing, quick insert and delete of table cells, improved CSS support, and support for positioned layers. For all your simple documents and website projects, Composer is all you need."
Amaya is another open-source HTML editor hosted by W3C (World Wide Web Consortium). Amaya is available for Windows, Unix platforms, and MacOS X. "It supports HTML 4.01, XHTML 1.0, XHTML Basic, XHTML 1.1, HTTP 1.1, MathML 2.0, many CSS 2 features, and includes SVG support (transformation, transparency, and SMIL animation)."
Macromedia Dreamweaver is the industry standard for web design and development. Dreamweaver is not free, but Macromedia does offer 30-day free trial downloads.
Notepad 2 is a simple Windows-compatible freeware alternative to Notepad and all of the above editors. It is great for editing code by hand because it features syntax-highlighting and colorcoding, and handy indentation guides to help you keep your markup properly nested and neat. The simple interface requires no training to figure out; just save your file with the proper suffix (.html, .css, etc.) and type away.
Taco HTML Edit is a full-featured HTML and PHP editor available for Mac OS X. This popular software is easy to use and it's freeware.
If you take the purist route and edit your websites by hand using one of the above text editors, you might find that you need a few more tools to keep your pages organized and up to web standards. With the following Firefox add-ons (you're using Firefox as your main browser, aren't you?) you might just find that you do not need complex software packages to create a beautiful, functional, state-of-the- art website. Here are a few we find useful, but there are more being developed all the time.
Firebug for Firefox is a tool that allows your view, inspect and edit source code for any page you have loaded in the browser. It adds a tiny button to the bottom-right corner of Firefox which you can click to expand and view the page sources.
Web Developer is an incredibly powerful tool which allows you to use different style sheets interchangeably to see alternative page views. It also allows you to view style sheets on other websites, to break down a page by its components, and to view your page as a screen reader might, among many other features.
If you use the above two add-ons regularly, you already have built in validators that will point out invalid HTML and tell you how to validate it, but if you do not, HTML Validator can also do that for you. Remember that a page should never be published with errors in its code. Always validate!
Even if you do use Firefox for all of your browsing needs, remember to check your pages in Internet Explorer and Safari to make sure that any visitors using those browsing will not have difficulties viewing your site. Not all code is compatible across browsers.