How to jump to another page in flask

two web pages in templates folder of flask.

@app.route('/')   # URL '/' to be handled by main() route handler
   def main():
   return render_template('index.html')
@app.route('/page') 
  def first():
return render_template('page.html')

index page html code

 <li><a href="">CS WORLD</a></li>

after clicking CS WORLD the new page is not opening