This page helps you discover the different special characters in HTML, and how to encode them. In Firefox, most characters will be correctly displayed in your browser. With Internet Explorer a lot less. Not yet tested with Safari.
HTML = HTML encoded, the way you would embed such a character in HTML (e.g.
á for á - use the HTML converter to encode your text)
URL = URL encoded, the way such a character should be specified in a querystring
ASCII= ASCII number code of the character