used or referenced in either HTML or XML, but when used in HTML, it is usually not flagged as an error by web browsers – some of which interpret it as a reference to the character represented by code value 128 in the Windows-1252 encoding for compatibility reasons. This character, "€", has to be represented as &#8364; in a standard-compliant HTML code. As a further example, prior to the publication of XML 1.0 Second Edition on October 6, 2000, XML 1.0 was based on an older version of ISO 10646 and prohibited using characters above U+FFFD, except in character data, thus making a reference like &#65536; (U+10000) illegal. In XML 1.1 and newer editions of XML 1.0, such a reference is allowed, because the available character repertoire was explicitly extended. Markup languages also place restrictions on where character references can occur. Compatibility issues In the initial versions of SGML and HTML, numeric character references were interpreted in relationship to the document character encoding, rather than Unicode. For Latin-script documents, numeric character references to characters between x80 and x9F in those documents will not be correct against Unicode, and must be recoded. HTML standards prior to HTML 4 supported only Western Latin script documents: the treatment of character references above #7F may vary between applications and national conventions. For example, as mentioned above, the correct numeric character reference for the Euro sign "€" U+20AC when using Unicode is decimal &#8364; and hexadecimal &#x20AC;. However, if using tools supporting obsolete implementations of HTML, the reference &#128; (Euro sign in the CP-1252 code page) or &#164; (Euro sign in ISO/IEC 8859-15) may work. As another example, if some text was created originally using the MacRoman character set, the left double quotation mark will be represented with code point xD2. This will not display properly in a system expecting a document encoded as UTF-8, ISO 8859-1, or CP-1252, where this code point is occupied by the letter Ò. The correct numeric character reference for in HTML 4 and newer is &#x201C;, because U+201C is its UCS code. In some systems, the named character reference &ldquo; may also be available. See also List of XML and HTML character entity references References HTML Unicode XML