I have installed React JS using `create-react-app`. The app has been installed successfully. But when I try to runt the app using `npm start` it compiles successfully but in the browser it shows the error `Requested resource "/" was not found on this server`. I don't know what is the problem, because everything was working perfect until that time. I was already working on a react js app and suddenly this problem occurred, and even when I created another app, I got the same error.

**Console**

```js
Starting the development server...
Compiled successfully!

You can now view resume-app in the browser.

  Local:            http://localhost:3000/
  On Your Network:  http://192.168.10.12:3000/

Note that the development build is not optimized.
To create a production build, use yarn build.
```