Utf-8 problem

I am correcting a large website that was created last year.  As I correct each page, I have it validated by the W3C markup validator page.  I have not had a problem finding the errors and correcting them until now.  The message I get is that the page failed validation because on lines 157, 187, 198, 254, 262, 274, 344, 366 contained bytes that could not be interpreted as utf-8 and the page could not be checked.  I have checked the page over several times, and do not understand what I am looking for.  I cannot see any code that is not allowed.  Please help.

The page is http://santafetrailnm.org/sfthistory.html<http://santafetrailnm.org/sfthistory.html>

Thanks.

Laura L Brewer, website designer
LauraLee, LLC

NOTE: Whenever possible, give the address of the document you were checking.