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Panašu kad Firefoxas nebe toks jau puikus tampa. Nustojo Java palaikyt. 
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Beginning with Firefox 52 (released March 2017), plug-in support is 
limited to Adobe Flash, and drops support for NPAPI, impacting plugins 
for Java, Silverlight, and other similar NPAPI based plugins.

If you have problems accessing Java applications using Firefox, Oracle 
recommends using Internet Explorer (Windows) or Safari (Mac OS X) instead.

https://www.java.com/en/download/help/firefox_java.xml