I'm answering this because most of these answers are old now, and this could use some up-to-date answers.
First, let's start with the free programs:
If you're a hardcore coder (not just for HTML and other web languages, but other programming languages, too, also great for text), I think Notepad++ is great. http://notepad-plus-plus.org . Also great for the coder, and more focused on web development, Aptana Studio (http://www.aptana.com/).
If you want an HTML5 WYSIWYG editor that is geared towards ease of use, and you're not much of a coder, BlueGriffon may be a good choice. (http://bluegriffon.org). There are plug-ins available that you'd pay for, but you'll find that out of the box for free it's very functional. But my main issues have been it doesn't produce clean code, and if I have to work with PHP, it doesn't work well at all with it (but I haven't tried the latest version).
Really, I have a hard time recommending BlueGriffon (which is based on NVU and Kompozer's code) if you want a professional web designer/developer to do the site later on. I used this for a long time, though. I would start out with the code to build a site quickly then break up the code for WordPress themes, but this program was particularly a pain, and though I mention it here, it's hard for me to recommend.
Paid:
For WYSISYG options, the ONLY thing I will recommend is Dreamweaver. I've had people tell me it produces bad code, but it's not been my experience. But I guess it depends on how you do your website. If you use WYSIWYG all the time, then yes, it might produce bad code. But I normally have split screen (both source code and WYSIWYG/design mode on the same screen) and still enter most everything in the source code editor. It works well when I'm working with PHP, too. I typically don't use Dreamweaver's built-in JavaScripts, but they're there if you want to use them. They can be very helpful for someone who doesn't know JavaScript and just needs certain functionality like validating fields on a form.
Dreamweaver is part of Adobe Creative Cloud. You can have it for as little as $19.99/month. You could also find older versions for sell on eBay that are pre-cloud that you wouldn't have to pay monthly for.
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