As of September 2017 the pixiv link shortener service has been discontinued. If you want to know why, the reason is given under the 【p.tlサービス終了の経緯について】 section.
Not sure if I told anyone before but it appears that there's a pixiv link shortener (created by pixiv I think).
You can see it here
Apparently if you save that link that looks like this "p.tlで短縮" in a gray bubble to your bookmarks, when you go on a pixiv page and click the bookmark it'll instantly give you the short link for that page. It's suppose to work on all browers. (Info in Japanese here)
FYI I tested it on and Firefox and Chrome and both work for me
So I guess I'll be changing the tutorial to use this link for sourcing pictures...