Always specify character encoding
As a Mac user and a user of "alternative" web browsers I have visited many websites where text does not display correctly. In almost every case that is caused by the website's author specifying an incorrect character encoding or not specifying a character encoding at all.
At times when I have tried bringing the problem to the attention of the developers I have been met by a lack of understanding. After all, they couldn't see a problem in their Windows-only world. Well, that is not the only platform used on the web, so you need to tell the visitor's browser which character encoding you are using.
David Baron's Why Web authors must specify character encodings explains this well.