Here is an example of on screen editing in action (using ColdFusion) to run the AnandTech.com site.
As with other solutions mentioned before, "The Administration area is built solely for Internet Explorer, due to some of the scripting used and advanced controls."
See: http://www.anandtech.com/IT/showdoc.html?i=1456&p=8 for screen shots of how they do it...
Sam