I'm running the w3.org HTML Validator tool on my site, which is a Zen Cart 1.3.8 site. It immediately states:

No Character Encoding Found! Falling back to UTF-8.

None of the standards sources gave any information on the character encoding labeling for this document. Without encoding information it is impossible to reliably validate the document. As a fallback solution, the "UTF-8" encoding was used to read the content and attempt to perform the validation, but this is likely to fail for all non-trivial documents.

Does anyone know the best way to fix this?

Thanks,
TJ