Do you actually have a element with a class of “hide”? Maybe you could share a link to your published project for diagnosis in browser developer tools?
Get them to download Chrome or Firefox so they can view sites with a modern browser if they can’t update the OS (Safari is bundled).
IX2 is setting the elements to display block. So you need to probably target the wrapper.
I could just target $('.header-wrap').hide(); then probably add a plain header back for those clients. If you wanted to do CSS feature detection on old browsers, use modernizr.