I think you are confusing language (English, French, Arabic, etc) with encoding (ASCII, UTF-8, UTF-16, Latin1, etc).

You do sometimes see mojibake in web pages, (question marks and □□ in place of the real text). These are caused by incorrect encodings. The web server tells the browser which encoding to use using the HTTP header Content-Type or using the <meta charset="UTF-8"> HTML element. You should always set the encoding rather relying on the browser guessing.