Check your locale.What's the output of locale? You must have an UTF8 locale (this encode every character in every language, other encodings are deprecated nowadays). Have you installed the required font (though Spanish characters are pretty standard)? DejaVu font is standard and is good to have. Sometimes web pages do not correctly mention the encoding they use, which can lead to these kinds of bugs. If you have problems with a specific page, firefox has an option to force a specific encoding (Menu Bar -> View -> Text Encoding); there was an equivalent option in chrome but I don't find it anymore.