At code point 01 to 1F, ASCII, ISO 8859-1 and Unicode contain control characters that cannot be displayed. Characters at these positions have been disabled here, and for good reason.

At code point 7F to 9F, ISO8859-1 and Unicode have invisible control characters. Most newer browser do display characters from Microsofts codepage Windows-1252 (Western European) here. Most notably something that looks like a Euro symbol at position 80. This, however, is dangerous. You cannot trust that these characters will be visible on other PCs than your own. While most modern browsers handle this "ISO 8859-1 to Windows-1252" replacement just fine, many email programs do not. A mail with a non-standard Euro sign may look crippled on the recipients computer. Btw, the "real" Euro-symbol is at code point 20AC in Unicode.