How to trap onclick event handler amidst onmouseleave, onmouseover, and onmouseout

[JJA]

I am trying to understand the event handling of this page (in order to
develop a new version with more AJAX code):

http://www.mortgagedataweb.com/MDWmaps/default.asp?config=providence_CW.txt

I think the essence of my question is how does a CLICK event on the
map image of this page get processed ... or how does the click event
get ignored by the other event handlers such that the page gets
reloaded.

More info:

Please note that the map on this page is defined by this element:

<input id="map" class="map" type="image" src="<%= image %>" width="<%=
cxmap %>" height="<%= cymap %>" onmouseover="toolTipStart();"
onmouseout="toolTipStop();" onmouseleave="toolTipStop();">

There is a function called reload() in the Scripts/Client_Functions.js
file which simply issues document.forms[0].submit() but I've been
unable to set a breakpoint on it to see how it is getting called.
Since there is no explicit onclick for this form element, I am
confused about how CLICKing on the map leads to the .submit in the
reload() function.

Hovering over a colored polygon on the map for about 1 second results
in an AJAX call to an .ASP page that returns XML, but I cannot see how
the CLICKing on a polygon of the map leads to another .submit of the
page. My goal for a new version is to develop a new AJAX call to
handle the click on the map (rather than the re-submit).

I've read lots about event handling in Javascript and I'm still having
trouble understanding what is going on in this case. Thanks in advance
for having a look at this and trying to help me.