It's because you need to put the thread's number at the %threadnumber% part of the URL (http://www.hfest.net/forum.html/thread/%threadnumber%/editForm).
For example. This thread's number is 10178 (http://www.hfest.net/forum.html/thread/10178/). Because of this, I will put 10178 instead of %threadnumber%, so: http://www.hfest.net/forum.html/thread/10178/editForm
Or you can simply write editForm at the end of the thread's URL.
