WYSIWYG stands for What You See Is What You Get, they are HTML editors that allow you to design your entire website without ever looking at any HTML code; but it has its drawbacks...
WYSIWYG HTML Editors or What You See Is What You Get editors are not as great as you think. These WYSIWYG Editors are tools which allow beginners to not have to learn HTML in order to create a website. Using these free web design tools, is not the best option, in order to create a successful website, you must know what you are doing and have a decent knowledge of HTML. Otherwise your website will not come out as you had hoped. Also, the use of these editors can make your page appear in an unwanted way to many other internet users than you see it. The file sizes when using WYSIWYG HTML Editors is much larger than if you design the entire site in HTML.
Actually, WYSIWYG Editors arent that bad if they are used by an experienced design, in conjuction with HTML Coding. This is because it WYSIWYG html editors allow the designer to see what it will look like in real time, and make quick changes to the HTML.
Some examples of WYSIWYG editors which are popular, and are the best WYSIWYG editors are Macromedia Dreamweaver MX, and Microsoft FrontPage. There are also other Free WYSIWYG HTML Editors out there, most of which I would never reccomend to anyone. The best WYSIWYG HTML Editor, judging by popularity would probably be CoolSite. Again I would not reccomend using any of the Free WYSIWYS Editors.