Charset=ISO-8859-1 causes a small question mark for apostrophes

I have two websites that are both set to use charset=ISO-8859-1. However, one site correctly displays the apostrophe in words like isn’t while the other website displays a small question mark in the place of the apostrophe. Any idea on why this is happening?

Thanks!

Possibly because the first one is using ’ and the other is using ´, the angled version that Word tends to substitute. I’ve found it’s a problem if I copy and paste text from another document, so I always do a “search and replace” for those characters.