CSS Tutorial CSS selector, attributes, Value _ Basics Tutorial

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

So basically, when it works with HTML pages, the text color between the body tag (the entire window content) is navy the font size is 0.8ems.

Length and percentage

CSS has many attribute values to specify units, but some basic units are used on some properties, before this is worth the attribute under them.
EM, such as FONT-SIZE:2EM, gives the size of the font, so 2em is twice times the size of the actual font.
PX, such as font-size:12px, is a pixel pixel unit.
PT, such as FONT-SIZE:12PX, is a unit of points pounds.
% For example font-size:80% is a percentage
Other units include PCs (12-point Western Type), cm (cm), mm (mm) and in (inches)

When the value is zero, the unit is not needed, for example: border:0 meaning has no border.

Web pages are not static, absolute media. This means that internal energy is scaled and distorted, and users should be allowed to adjust their preferred ways, including font size and screen size.

Because of this, it is recommended to use "em" and "%" on the font-size (width and height), compared to the PX can not be in most browsers to change the size, so use less, you can use in the size of the border.