def html_quote(line):
    """Change HTML special characters to their codes.

    Follows ISO 8859-1 Characters changed: `&`, `<` and `>`.
    """
    result = line
    if '`' not in result:
        result = line.replace('&', '&amp;')
        result = result.replace('<', '&lt;')
        result = result.replace('>', '&gt;')
    return result
