The � character is a result of importing information from a CSV file that uses a different character encoding than your web site.
We use the character encoding called UTF-8 on your web site. This is the international standard and supports the characters from almost all written languages. However, Windows, Macs, etc traditionally use Windows-1252 or Mac OS Roman.
The standard characters like A to Z and numbers are the same in all three character encoding standards but when you use characters like curly quotes, mdash (long hyphen), etc, they don't map correctly between the different character encodings.
What you will need to do is to convert the character encoding from what it is now to UTF-8. Once you have done that and re-imported the CSV, the question mark characters will disappear and be replaced with the correct characters.
This online tool should convert the file for you.