CSS selector, attribute, and value in CSS tutorial

Body {
Font-size: 0.8em;
Color: Navy;
}
The above indicates setting the font-size font size and color font color for the body selector.

So basically, when it works with an HTML page, the text color between the body tag (content in the entire window) is Navy and the font size is 0.8ems.

Length and percentage

There are many attribute values in CSS to specify units, but some basic units are used in some attributes. Before that, they are worth attributes.
EM: for example, font-size: 2em gives the font size, so 2em is twice the actual font size.
Px, for example, font-size: 12px is the unit of pixel.
PT. For example, font-size: 12px is the unit of the points pound.
% For example, font-size: 80% is a percentage.
Other units include PC (12-point Spanish active text), CM (CM), mm (mm), and in (inches)

When the value is zero, no unit is required. For example, border: 0 indicates no border.

Webpages are not static and absolute media. This means that internal scaling and deformation can be performed, and users should be allowed to adjust their preferred methods, including font size and screen size.

In this case, we recommend that you use "em" and "%" on font-size (width and height). In contrast, PX cannot be changed in most browsers, so use less, it can be used on the border size.