Here are some free WYSIWYG HTML Editor software and online tools. You can edit the output content and HTML source code and preview it.

How to build a desktop WYSIWYG editor with WebKit and HTML 5 Web technologies are increasingly being used on the desktop to bring richer … ...

CoffeeCup HTML Editor has a friendly way about it. Tabs along thetop and sides of the window put the three main views (Code Editor,Visual Editor, and Preview) right at your fingertips.