However, looking at it, a user couldn’t see a difference — unless they looked at the source code.
Obviously hackers got in through a hole and hacked the source. But invisible, what good is it? Well, for one thing, hidden like that, it’ll take some time for people to catch it (hello, Webmaster, that hack is still there!). But the important thing for the hackers is that a search engine like Google will pick up the links as they crawl the site. And, since Gore’s site has such a high PageRank, Google will rank the links higher.
It pays to post more often, Al! You haven't posted to that site since 2006, and perhaps you would have noticed something if you'd posted more recently. At any rate, the issue is still there so hopefully the Webmaster will take care of it soon!