I disagree. I think he understands oncliick. He just doesn't understand what HTML ALONE does.
He doesn't seem to be aware that rolling over an image *WILL* produce the title display.
As I noted, he could use alert( ) for this except that it's so obsolete. But for his purposes, that may be perfectly okay.
Creating a full blown tooltip is a lot more work. Though there are ways to make it simpler.
An optimist sees the glass as half full.
A pessimist sees the glass as half empty.
A realist drinks it no matter how much there is.