O co chodzi z "Byte-Order Mark" (BOM). W Walidatorze W3C pokazuje mi się informacja:
The Unicode Byte-Order Mark (BOM) in UTF-8 encoded files is known to cause problems for some text editors and older browsers. You may want to consider avoiding its use until it is better supported.
The following missing or conflicting information caused the validator to perform guesswork prior to validation. If the guess or fallback is incorrect, it may make validation results entirely incoherent. It is highly recommended to check these potential issues, and, if necessary, fix them and re-validate the document.
Czym to może być spowodowane ??