Nvu/KompoZer grew out of the Mozilla Composer WYSIWYG editor project with the support of Linspire, and aims to provide an open source alternative to commercial products like Macromedia Dreamweaver and Microsoft FrontPage.
KompoZer is for everyone, including novices with no HTML knowledge. However, if you do know HTML, you can directly edit the HTML code as well, and you can easily switch back and forth between the graphical WYSIWYG view and the source code view. In fact this is a good way to learn HTML, since you can see and edit the HTML created by the graphical editor.
KompoZer uses Mozilla's Gecko engine to promptly provide views of how a web browser would show your work. An easy to set up and easy to use FTP client is available so that you can transfer your pages to a web server and keep them up-to-date with minimal hassle.
KompoZer is free. You can download it here and start designing right away.