I have the same version of FireFox and having no problems. What FSH version are you using? I have version 1484 (at top under FSH Settings Tab in Preferences)
So I have written in a ticket a possible solution to the problem.
quote ticket:
"Would it be possible to replace "72.29.91.222" with "huntedcow.cachefly.net/fs" this should fix thousends of pages all at once. So I don't have to waste days on fixing all of them manualy.
This suggestion is/was less about the 'monster arena', and more about wanting to kill monsters MUCH higher level than me. Looking at the UFSG, I can get the stats to kill a level 1800 monster... WHY?! A player at 300 shouldn't even come close. (I'm not talking about 1-hitting. 1-hitting used to be a privilege, now people assume it to be a right (it's not).
This would be more about gathering data about overpowered gear and under-powered mobs, and ask for a nerf/buff accordingly.
Are you using buffs from your level only or from higher levels? Try using just the buffs from your level and check the stats, not any buffs that you can acquire.
So you would rather make a monster arena to confirm that you know how to kill a creature than just check the stats of the creature to see if you can kill it? Seems like a waste of time to code this.