Okay, we're starting with the basic url.
http://www.ecocitycraft.com/forum/t...nks-without-using-a-shortening-service.72611/

This is a really long url and it won't work when pasted into minecraft.

so we're going to take the thread number, which I marked as the red part of the url
http://www.ecocitycraft.com/forum/threads/shortening-forum-links-without-using-a-shortening-service.72611/

And we're going to paste that into
http://www.ecocitycraft.com/forum/threads/<number>/
So it will look like:
http://www.ecocitycraft.com/forum/threads/72611/


To make it even shorter, remove the http://www. part of the url. You will end up with ecocitycraft.com/forum/threads/72611/

This url works in-game without a problem.