CSS Values and Units

Is a whole number such as 1024 or -55.

represents a decimal number — For example, 0.255, 128, or -1.2.

For example, 50%.

Percentages are always set relative to some other value. You need to be aware what it is a percentage of
For example,
IF -> you set an element's font-size as a percentage,
THEN -> it will be a percentage of the parent's font-size
IF -> you set an element's width as a percentage,
THEN -> it will be a percentage of the parent's width 

Can be any of the following:

• Color keywords identifiers such as purple, red

• Hexadecimal Values

• rgb(0-255, 0-255, 0-255)

• rgba(0-255, 0-255, 0-255, 0-1) last value is for transparency values

• url(filename.png)

Can be any of the following:

• top
• left
• bottom
• right
• center

Typically consists of two values

1. first sets the position HORIZONTALLY,
2. second sets position VERTICALLY

Quoted in ""

.box::after {
  content: "This is a string. I know because it is quoted in the CSS."
}
Copy

Can be any of the following:

• rgb()
• url()
• calc()