cross browser - gog.com's login link missing only in Firefox (for HTTP) -

gog.com has http site (http://www.gog.com/) , https site (https://secure.gog.com/).

when visit https site in firefox, login/sign-up link visible:

when visit http site in firefox, link missing:

but when visit http site in chromium, link visible:

so gog.com doesn't seem hide login link in general on http. in fact, if disable css, can see login form on http variant on firefox, too:

i contacted gog.com support, not able reproduce it.

i tested 3 different firefox installations on different systems, , never saw login/sign-up via http. me?!

i checked source code firebug. http, relevant part seems be:

<div class="nav_user">   <div class="nav_empty not_logged"></div> </div> 

for https, looks like:

<div class="nav_user">   <div class="nav_link nav_account nav_login" data-hoverclass="hover_acc">     <span class="nav_login_icon"></span>     <span class="nav_text">login / sign-up</span>     <div class="nav_hover"></div>   </div>   <div class="nav_cart_h">     <div class="nav_empty"></div>   </div> </div> 

does have explanation this? why work in other browsers not in firefox?

edit: other things on http site don't seem work in firefox either (but on https without problems). example can't use big carousel on home page: clicking navigation arrows doesn't anything, clicking @ 1 game neither.

so these problems related javascript? firefox have security features disallow functions on https or that?

for whatever reason, gog.com requires local storage http (but not https).

so about:config setting dom.storage.enabled needs true.

(similar problem js on anime.stackexchange.com , japanese.stackexchange.com)