Yes, we can use it all together, but there should be no duplicate properties for the same tag, class, or id across the CSS.
Inline CSS has the highest priority, followed by Internal/Embedded CSS, and finally External CSS, which has the lowest priority. On a single page, you can declare many style sheets. If multiple style sheets describe styles for an HTML tag, the order listed below will be used.
There are three techniques to include CSS in HTML documents: Inline - inside HTML elements, using the style property. Internally, a style> element in the head> section is used.
You can convert inline styles to CSS rules that live in the document's head or in an external style sheet to make your CSS clearer and more organised. Select Selection > Convert Inline CSS to Rule from the context menu.
The term "inline CSS" refers to CSS that is loaded in the HTML's head> tag. This is faster than having the visitor download the CSS files from the server; but, if all of the site's CSS is displayed inline, the entire site's load time will be slowed.