Forum OpenACS Q&A: Re: Multiple Language Static Pages
There probably are such headers, but you need not use them. What matters is properly specified charset, which in your case seems to be Windows-1252 for both English and Spanish pages. Configure AOLServer to return this charset in server response headers, and you're fine.
You can view server response headers using e.g. Sam Spade "browser". Currently you specify no charset there, only in the page headers. It's better to specify the charset in both headers, and definitely NOT different charsets, so check it.