I’ve finally worked out how to drive purple-url-handler. Strictly
John worked it out, so I
will stand
on his shoulders, but for some reason it would not work for me
and I now know why and have a workaround.

First you need an XMPP URI on a web page. Some thing like:

xmpp:chrisg_fans@muc.im.sun.com?join

will when clicked in a browser that has the right helper,
something OpenSolaris has had for some time, will take your IM client
to that room. However with pidgin that is only the case if that room
is available in the first XMPP server listed in your list of
accounts. So given that this room is on Sun’s IM server with the list
of accounts looking like this:

It
will try and connect to the first XMPP server listed, which is google
and hence fail. Changing the order to be:

and
then logging in and out and now the link will work. You can drag and
drip the entries in pidgin.

Source : http://blogs.sun.com/chrisg/entry/pidgin_url_handler_and_xmpp