Fix bugs in website to validate with w3c validator - repost

I need to fix all bugs in website to validate with w3c validator, at first gives this errror: Sorry, I am unable to validate this Document Because it Contained on line 154 one or more bytes That I can not interpret as utf-8 (in other words, the bytes found are not valid values ??in the specified Character Encoding). Please check Both the content of the file and the character encoding indication. The error was: utf8 "\ XF1" does not map to Unicode I need to fix this and other bugs that come out when this error is corrected