Slightly confused (Score 1)

I have what may be a silly question... I tried to post the link to this story to some friends, and they couldn't pull it up because it said registration was required. So then I pointed them to the slashdot article, and had them click the link, and it still said registration required. But then I had them go to the slashdot home page and click the same link, and the article appeared, no mention of registration. I tried to do the same thing and got the same result as they did. Why is this? I'm just curious, as it seems to be an odd behaviour...