Flask: Making my first web site

[Truman]

Any idea where to start from if I run to this 404 error.

Error:
Not Found

The requested URL was not found on the server. If you entered the URL manually please check your spelling and try again.

I started local server without a problem

Output:
(venv) C:\Python37\kodovi\Projects\flask_official_tutorial\flask-tutorial>flask run
 * Serving Flask app "flaskr" (lazy loading)
 * Environment: development
 * Debug mode: on
 * Restarting with stat
 * Debugger is active!
 * Debugger PIN: 318-132-539
 * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
127.0.0.1 - - [03/Oct/2019 23:04:36] "GET / HTTP/1.1" 404 -
127.0.0.1 - - [03/Oct/2019 23:04:36] "GET /favicon.ico HTTP/1.1" 404 -

I'm following flask docs tutorial.