I recall seeing something like that last week. The Web site of the manufacturer was so badly implemented that I left immediately.
The problem with programs like that is twofold:
Most tools like that create very bad code. Bad HTML, bad PHP (or whatever other language might be implemented). Look at the abominable garbage that comes out of tools like FrontPage.
You don't learn. If you go through school having somebody else do your homework, you'll be forever ignorant. The only way to learn to write good code and develop good Web sites is to do the work.
I don't want to overstate the case; there are tools that can be helpful. Any decent HTML editor should colorize the code to help you spot errors. Many of them understand PHP syntax and will automatically colorize that. A tool such as Quanta, for Linux, is useful in that it produces an object-tree view of an HTML document and can help you spot dumb nesting errors. A good HTML checker is always useful.