With most WYSIWYG programs, you can get cluttered scripts and other problems which can hurt your site in terms of search engine ranking. Sure, it may look good to the customer and work okay in Internet Explorer, but for search engines and users of other browsers, your site can look like a jumbled mess.
“WYSIWYG Versus Coding: HTML With A Purpose” by Jim D. Ray explains the benefits of hand-coding and some of the problems you might get with WYSIWYG editors.
“After years of working with entrepreneurs who developed their first web site using an image-based editor, the new world of internet marketing has placed a stronger emphasis on web development that conforms to technical concerns such as search engine optimization and multi-browser compatibility.”
“Although a relatively simple programming language, HTML is a diverse subject with many facets that can be used to create a dynamic, rich web presence.”