I did some troubleshooting of the map URLs not being clickable in my html output. I tracked it down to an extra 'a' prefixed to the value for the 'usemap' attribute. (or a missing 'a' on the map name attribute; note how the 'a' is in the id attribute)
<div class="center"><img src="../../d2/d83/FILE.png" border="0" usemap="#aIDENTIFIER" alt=""/></div>
<map name="IDENTIFIER" id="aIDENTIFIER">
<area ... />
<area ... />
<area ... />
</map>
Is this a bug?
(Doxygen 1.8.20)