Speaking of jargon, what does "on main" mean ? EDIT : This is the issue with «write like you talk / being too 'cute'» : with too much slang you're losing part

Speaking of jargon, what does "on main" mean ? EDIT : This is the issue with «write like you talk / being too 'cute'» : with too much slang you're losing part of your target audience, especially as the blogpost gets older ! Other problematic examples in there that I got, but barely : «top text bottom text» (though thankfully solved by the author following their own advice about multimedia examples), and «galaxy brained». (Great advice otherwise.)