When you write your HTML, you should use proper capitalization. You write your content in sentence case, which means lowercase, except for the first letter of a sentence or proper names.
If you want to use all caps in a heading, for example, rather than write it in the HTML, use the ‘text-transform’ property in the CSS.
Don’t do this:
<h2>ABOUT</h2>
Do this instead:
<h2>About</h2>
And style it on the CSS:
h2 {
text-transform: uppercase;
}
In the first (wrong) example, some screen readers will read “A‑B‑O‑U‑T” rather than the word “about”.
And also, you will make your life easier if you use the text-transform property because it’s easy to reverse in case you change your mind.