Thanks, but I think what you are telling me is that I have to know a whole lot about Ajax before I can make this work.
Your example. a onclick="tooltip.ajax.... resulted for me in a "Failed ot get data." message.
I presume that you were referring to the third way to set tooltip content in the link to which you referred me.
Those details appear to indicate that I need to set up some type of xml file or ashx something-or-other file.
The "Details about each Ajax setting" go way beyond my skillset.
As I wrote in my original question, I do not use asp.net or ajax.
There are just not enough hours in the day for me to master another programming environment in order to make this work.