Occasionally you may run into a situation in which the validator complains about characters in the prolog which do not appear in your preferred text editor. These characters, which appear as the characters  when you view the source from a browser, are a Byte Order Mark. In documents encoded using the UTF-16 character encoding format, the Byte Order Mark specifies which digit in a given byte is most important. When improperly applied to documents encoded in UTF-8, however, the Byte Order Mark causes the validation error that brought you to this page. Many common text editors, including Notepad, silently add a BOM to documents that are encoded in UTF-8. In order to remove the BOM, you may need to use a hex editor.