If you publish your iWeb site via FTP to a web host other than .Mac, some characters may appear incorrectly when viewed in a browser. For example, some characters may show up as question marks.
This can happen when an FTP program misinterprets characters on your webpage. Because FTP programs and host servers don't always adhere to the same standards, changing your FTP and/or host server preferences to use UTF-8 text encoding may resolve this issue (iWeb uses UTF-8 text encoding).
If that does not help, check the support documentation provided by your Internet service provider or web host to learn how to change applicable settings on the host server.