The browsers didn't block your very old Java 6 update 7 from 2008. It stopped working a couple years ago, before the security blocks started, because browsers adopted a standard API to work with Java that your old Java version doesn't use. That's why you can't unblock it, it's a compatibility issue not a block issue.
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java.com/en/download/faq ··· ugin.xmlsaid by Java website :
Starting in Firefox 3.6, Mozilla foundation will drop support on OJI (Open Java Virtual Machine Integration) and will only support the standard NPAPI and NPRuntime interfaces. The Java Plug-in which is in Java version 6 update 10 or newer versions supports the NPAPI and NPRuntime interfaces. Therefore, starting with Firefox 3.6, Java-based applets will NOT work unless you are running Java version 6 Update 10 or newer.