Confused a little bit
I would say, but can you give an example of a such message so that I know what you mean exactly.
Did the translation appear over there yet? I don't see it.
Glacious, note that you should translate, not customise. The content of your translation seems very different (there are no per-browser instructions, as far as I can see). If you want to change the message in MediaWiki, you have to propose so to the developers.