This is an exceptionally cool piece of work, which is entirely by David Flanigan. Make sure FireBug is turned off; it seems to get in the way. Then put your mouse over the links below for a few seconds.
What's going on is this :
* the .html source file doesn't have any javascript (!).
* the linkdetails.js attachs mouseover handlers to all the links.
* when the mouseover happens, the http.js routines fetch the
headers of that file asynchronously ...
* and use the Tooltip.js and Geometry.js routines to pop up a message.
but, the 'same-source' policy restricts the javascript from getting files that aren't on this server, so for other files all it can do is report what it knows - the URL.
