From here: http://forums.netbeans.org/ptopic37586.html
NetBeans 6.7.1 was the last version
with support for the visual desinger.
Be aware that you will able to
visually work with JSF files, not
plain JSP.
Maybe, Using Netbeans 6.9.1, you could check the following out:
There is a plugin called 'Web Preview' that will open the file in your external browser for a preview and allow you to immediately see the changes you make (after refreshing the browser).
But as far as I'm aware there isn't a WYSIWYG web page designer, and I can't seem to find one in the Plugins after a 'quick' search in Google.
Maybe you could look here for alternatives:
https://stackoverflow.com/questions/5833/looking-for-wysiwyg-html-editor