Pale Moon forum

tested it with blank Palemoon 27.9.4 and 27.6.2 and 26.5.0_AtomXP portable
even Firefox 52 ESR does not work anymore
Firefox 60 opens the site.

now the question is why and if there is a solution to make that site work again

I am not sure why ESR52 can't open the website but Pale Moon 28 Unstable can. Also, there are already threads in existence about userstyles.org.