ActionHTML rule of Work- class is a final rule in 6.3 SP1. As per the rule, it supports "IE Only". However, as per the Platform Support guide, 6.3 supports FireFox browser. Please see the attachments.
Is there a HotFix available that overrides this rule in order to support other browsers? Also, are there any other final rules in 6.3 that are only IE specific? wondering if the platform support guide is correct?
It's possible that rule (and others like it), defaulted to IE once created. Especially if they were originally created years prior to 6.3. But it may still work under an alternate browser. Your mileage will vary.
But for this specific scenario, since you're on 6.3 SP1, then you should migrate to use pyActionArea. This should remove any doubts regarding cross browser support.