Unable to change Font

Hi,

I have a problem to set up the language
I did use

@font-face {
      font-family: english;
      src: url("<%= current_language.get_font_url %>")
format('truetype');
      }
      html {
        font-family: english;
      }

%= current_language.get_font_url => app_data/language_english/
font.ttf

but it does not change the current font.
can anyone help me..

Thanks