How to center a div in just 4 lines of code!!!

Hey coders, Let's add a empty container in center of web page in just 4 lines of code.

1.First we need index.html and
a style.css.
2.Let's create a empty div in
index.html file. And give
demo as class name.

1. Now give some style to this
   empty div to we can see it.
   

2. Let's get it in center vertically and also horizontally in just four lines of code.
   5.Code is below
   

6.Stay tuned with me I am sharing all my trick and tips.
🙏 Thank you for reading
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