user1361: I’m not able to use any functions that require JavaScript on (meta.)anime.stackexchange.com, i.e.: I can’t vote, can’t comment, the SE notification bar at the top doesn’t work, no hover pop-ups for users/tags, etc.
It works for all other Stack Exchange sites I use.
I tried it with a different Firefox profile, tried it as guest, cleared cache etc. When I logout and try to vote up a question, nothing happens. If I try this on any other SE site, I get the Thanks for the feedback! pop-up, asking me to login.
In Chromium everything seems to work fine.
I’m using an older Firefox version (20.x) currently (can’t test it with the current version atm). If this should be the reason for the broken JS, then why is this not the case for all other SE sites? Tested it with the current version (23.0.1) on a different OS: same problem there, too.
EDIT: Updates

In the error console, I get the following error when reloading the page:


TypeError: localStorage is null
  Source: http://sstatic.net/js/third-party/japanese-l-u.js?v=2
  Line: 32  
I have the very same problem with japanese.stackexchange.com also: no voting etc. possible in Firefox
Thanks to the error message about localStorage, I now know what’s causing this bug: the about:config setting dom.storage.enabled = false (it needs to be true if you want to use any JS functions here)


user1503: We only support the last two releases for FF, which is 22 and 23. However, while we don't guarantee it, older versions usually work.
In this case, it's probably something to do with the Hiragana support which is also enabled on Japanese SE - and we can't fix that for unsupported browsers. The best thing to do is just upgrade FF, if you don't want to do that, try a more recent version of another browser.
Still, at least for the time being, the version you're using will probably work on other sites, at least where Hiragana (and possibly MathJax) aren't loaded.
For reference, here's our list of supported browsers.
Edit
Reproduced by disabling local storage on FF - escalating to the devs.
This was in fact an issue in the Japanese support user script, which uses local storage to store preferences and does not deal with it being disabled, causing JS to break entirely - even on current browsers. As we strongly recommend but don't require local storage to be enabled, a fix has been pushed that will go out in the next build. 

1361: <p>I’m not able to use any functions that require JavaScript on (meta.)anime.stackexchange.com, i.e.: I can’t vote, can’t comment, the SE notification bar at the top doesn’t work, no hover pop-ups for users/tags, etc.</p>

<p>It works for <a href="http://stackexchange.com/users/1739979/unor?tab=accounts">all</a> other Stack Exchange sites I use.</p>

<p>I tried it with a different Firefox profile, tried it as guest, cleared cache etc. When I logout and try to vote up a question, nothing happens. If I try this on any other SE site, I get the <em>Thanks for the feedback!</em> pop-up, asking me to login.</p>

<p>In Chromium everything seems to work fine.</p>

<p><s>I’m using an older Firefox version (20.x) currently (can’t test it with the current version atm). If this should be the reason for the broken JS, then why is this not the case for all other SE sites?</s> Tested it with the current version (23.0.1) on a different OS: same problem there, too.</p>

<p><strong>EDIT: Updates</strong></p>

<p><ul>
<li>In the error console, I get the following error when reloading the page:</p>

<blockquote>
  <p>TypeError: localStorage is null<br>
  Source: <a href="http://sstatic.net/js/third-party/japanese-l-u.js?v=2" rel="nofollow"><a href="http://sstatic.net/js/third-party/japanese-l-u.js?v=2" rel="nofollow">http://sstatic.net/js/third-party/japanese-l-u.js?v=2</a></a><br>
  Line: 32  </li>
  <li>I have the very same problem with <code>japanese.stackexchange.com</code> also: no voting etc. possible in Firefox</li>
  <li>Thanks to the error message about localStorage, I now know what’s causing this bug: the about:config setting <a href="http://kb.mozillazine.org/Dom.storage.enabled" rel="nofollow"><strong>dom.storage.enabled</strong></a> = <code>false</code> (it needs to be <code>true</code> if you want to use any JS functions here)</li>
  </ul></p>
</blockquote>
 1503: <p>We only support the last two releases for FF, which is 22 and 23. However, while we don't guarantee it, older versions usually work.</p>

<p>In this case, it's probably something to do with the Hiragana support which is also enabled on Japanese SE - and we can't fix that for unsupported browsers. The best thing to do is just upgrade FF, if you don't want to do that, try a more recent version of another browser.</p>

<p>Still, at least for the time being, the version you're using will <em>probably</em> work on other sites, at least where Hiragana (and possibly MathJax) aren't loaded.</p>

<p>For reference, here's our <a href="https://meta.stackexchange.com/questions/56161/which-browsers-are-officially-supported-and-what-else-do-i-need">list of supported browsers</a>.</p>

<p><strong>Edit</strong></p>

<p><strike>Reproduced by disabling local storage on FF - escalating to the devs.</strike></p>

<p>This was in fact an issue in the Japanese support user script, which uses local storage to store preferences and does not deal with it being disabled, causing JS to break entirely - even on current browsers. As we strongly recommend but don't <em>require</em> local storage to be enabled, a fix has been pushed that will go out in the next build. </p>
