A recent survey concluded that 40% of the web population are non-English speakers. Many of these use non-English version web browsers. Don't assume that everyone's default character set is the same as yours - explicitly state your intended character set. For western characters this can be achieved with:
|<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">|
I've seen many websites from large reputable companies that fail to specify the character set, and use extended ISO characters for the single apostrophe, em-dash, copyright or trademark symbols. International browsers, especially those in the Far East will fail to render such characters, replacing them with "?", a square box or in some cases combine them with the following byte to form an oriental character. Specifying the character set explicitly prevents this problem.