It's the standard title attribute:
Code:
<img title="Frostbite Winterfest" src="slide_StHelensWoodCarvers111Chamber.jpg" border="2" alt="Frostbite Winterfest" >
So you could do, for example (scroll the code block to see it):
Code:
leftrightslide[0]='<a href="http://www.clareco.net/special_events/frostbite/2011_fb.htm" target="_parent"><img title="Frostbite Winterfest" src="slide_StHelensWoodCarvers111Chamber.jpg" border="2" alt="Frostbite Winterfest" ></a>'
To repeat, alt is not for "showing up". Sometimes it does in IE. Apparently not in an iframe (it's actually more complex than that*). What alt is for is when there's a problem with the image. Then the broken image token is shown, along with the alt text if any.
Use title for this. Keep the alt too though, it will help you if any image ever is missing - to track it down as to which one it is.
*It will in an iframe in IE less than 9, and in IE 9 if both pages are in quirks mode. But if the top page is in standards mode (your current one is), in IE 9 it will not. No other browser will do it in any mode on any page inside or out of an iframe. In any case, the standard attribute for this is title. Use it and you will be OK in any browser, including all IE in any mode.
Bookmarks