Q:

how to use two fonts for two different languages like english and persian (farsi)? 

imagine that you want to design a website that learns English to Iranian people (Persian (Farsi) language) .  English and Persian (Farsi) doesn't have any similarity in alphabet because Persian is RIGHT TO LEFT and English is LEFT TO RIGHT and completely are different .  i didn't find any tags to set one font for all Persian (Farsi) words and other font for all English words .  for example set B-Nazanin for Persian and set Times New Roman for English automatically that don't need to define font for every word every time .  just define once these fonts .  what can we do ? 
thanx

A:

One possible option is to give a lang="fa-IR" attribute/value to the <html> or to any other elements within the document when the website is shown in persian language. 
Hence you can override CSS declarations by using [lang|="fa"] selector. 
For instance:

[lang|="fa"] p { font-family: "B-Nazanin"; }
<html lang="fa-IR">
  <p> سلام دنیا </p> 
</html>

Or:

p[lang|="fa"] { font-family: "B-Nazanin"; }
<p>Hello World!</p>
<p lang="fa-IR">سلام دنیا!</p>

A:

using style content by language in HTML is to use the :lang selector in your CSS style sheet.   ex : 
:lang(ta)   {
    font-family: Latha, "Tamil MN", serif;
    font-size: 120%;
    }

and dont forget use lang  in  you HTML code 
<p lang="en">Ceci est un paragraphe.</p>

