Firefox's Web Console displays this intriguing error:

ReferenceError: none is not defined main.js line 2 > eval:1:1

• <anonymous> https://webgis.ci.brookfield.wi.us/BrookfieldWebMap/js/dbootstrap/main.js line 2 > eval:1
• g https://webgis.ci.brookfield.wi.us/BrookfieldWebMap/js/dbootstrap/main.js:2
• r https://webgis.ci.brookfield.wi.us/BrookfieldWebMap/js/dbootstrap/main.js:46
• l https://webgis.ci.brookfield.wi.us/BrookfieldWebMap/js/dbootstrap/main.js:46
• c https://webgis.ci.brookfield.wi.us/BrookfieldWebMap/js/dbootstrap/main.js:46

Seems as though it could be significant, but I have no idea how to figure out what might cause it.

Do you recall the last version of Firefox where ARCGIS worked normally?

Previous system was an Acer Win7 machine running (I think) v54. I liked the older interface and stopped the upgrades.

Hmm, that version is nearly 3 years old, so probably the site was working in a more recent version of Firefox. Seems we need someone to test in a bit more depth to determine whether it was caused by a recent change in Firefox.

So at least I know it is not just me. Appreciate the attention.

Firefox 45 gives the same error in the Web Console, but shows some code:

ReferenceError: none is not defined
<anonymous>
 main.js line 2 > eval:1
g()
 main.js:2
.cache["xstyle/load-css"]/</</r()
 main.js:46
l()
 main.js:46
.cache["xstyle/load-css"]/</w/</e[c]()
 main.js:46
 main.js line 2 > eval

The site has property tax information available and I last used it last year around this time. It *has* changed since last year. So perhaps the new site just isn't Firefox Friendly?

There is a page for reporting sites incompatible with Firefox, in case you want to post it over there for someone to look at:

https://webcompat.com/issues/new

Listed it there, but I don't have a github account so left it as anonymous.

Tried a different 'user agent', didn't help.

Filed https://bugzilla.mozilla.org/show_bug.cgi?id=1605803.

Thanks for the help guys.