Mismatched Character Encoding

If you choose to write in a word processor, it will add “smart quotes,” em dashes–long dashes like these–and even symbols like copyright, ©, or single-character ellipses…

Pasting special characters into your XHTML source without a proper character encoding, such as UTF-8, will cause errors such as the ones you see on this page (which is improperly encoded using the old ASCII-based character set, ISO-8859-1).