def _create_index_content(words):
    """Create html string of index file.

    Parameters
    ----------
    words : list of str
        List of cached words.

    Returns
    -------
    str
        html string.
    """
    content = ['<h1>Index</h1>', '<ul>']
    for word in words:
        content.append('<li><a href="translations/{word}.html">{word}</a></li>'
            .format(word=word))
    content.append('</ul>')
    if not words:
        content.append('<i>Nothing to see here ...yet!</i>')
    return '\n'.join(content)
