"alt" is an attribute which is only available for img tags, for
example a thumbnail image located inside the link.
So, if you are using thumbnails inside your links, you can use the
following linkMapper function to grab the description from the "alt"
attribute of the thumbnail if no "title" attribute is available on the
link:
function(el) {
return [el.href, el.title || el.firstChild.alt];
}
Also, I think there is a way to disable the tooltips display using
javascript, but I don't know exactly how.