How do I use the Align property in a CSS file?

I introduce a demo.css in an HTML page, others are normal, but the Align property of the H4 tag is not displayed correctly. Is it because you can't write align in a linked style? There is no problem in writing inline style.
The code is as follows:
Here is a few lines of code for the HTML page

<H1 style= "Color:blue" > Front-end Engineer: javascript,php,css! <br/> 
One more.



Here's another one:



Can you help me look?? I'm a novice too.

It should be text-align:center; But align can't do it.

<! DOCTYPE html>
But it's important to note that all 


Text-align, it should be the attribute you're looking for.