I believe the way to do this is to select 'onmouseover' in the extented properties area of the object.  In the value, you can just use a quoted string or something more complex using the expression editor.  Unfortunately, when I tried this on a button it didn't do anything even though the onmouseover setting is in the HTML code.  Can anyone else figure out why?

Here's the HTML

<input onmouseover="This button will delete all data in the database" type="submit" name="wt13" value="Delete All Data Records" id="wt13" class="Button" />

Thanks Curt.

I assume you need to invoke a javascript function, for example, "alert('This button will delete all data in the database');" for the value.

I tried the suggestion to link the text and used the title for the text and it worked fine with ajax as the method. 

After some more research you don't need any javascript or ajax.  Use the 'title' property instead of 'onmouseover' and you'll get the tooltip.  You have to type 'title' in the extended properties box since it is not in the dropdown.  I used it on a button and a container and it worked perfectly for me in IE9 and Chrome.

Thanks, Curt.

It worked for me too.