How to filter UTF-8 encoded content

How to filter UTF-8 encoded content

eg.

in a web
use this rule

/ip firewall filter
add action=accept chain=forward comment=“” content=xxxxxxx disabled=no protocol=tcp

if the web encoded is UTF-8, we can’t fiter anything.

HOW DO ???

eg URL
http://www.123cha.com

BTW ,the content is english, eg “ip”