css terms and concepts

 

.vocabulary{
    height:99px;
    color:transparent;
}

 

Attributes

The above shows that the height and color in the css code are attributes.

 

value

The 99px above is the value

Integer value: such as 1 in z-index:1
Value: 1.5 as in line-height:1.5
Percentage value: such as 50% in padding:50%
Length value: such as 99px
Color value: such as #999

 

keywords

The above transparent, the keyword refers to the key words in css, the keywords that can be used by all css properties

 

variable

There are currently limited variables that can be called variables in CSS. The currentColor in CSS3 is a variable, which is very useful.

 

length unit

　　Such as px, em

　　Relative length units are divided into relative font length units and relative viewport length units

　　　　Relative font length units, such as em and ex, and rem and ch in the new world of CSS3

　　　　Relative viewport length units such as vh, vw, vmin and vmax.

　　Absolute length unit: the most common one is px, and pt, cm, mm, pc, etc., you can understand it, the practicality is close to 0

 

time unit

　　 such as s, ms

 

angle unit

　　 Such as deg, rad, etc.

 

function symbol

　　The value is specified in the form of a function (that is, the one enclosed in parentheses), color (rgba, hsla), background image address (url)

 

attribute value

　　Everything after the attribute colon is collectively called the attribute value

 

statement

　　The attribute name + attribute value is the declaration

color:transparent

 

declaration block

A declaration block is a series of declarations enclosed in curly braces

{
    height:99px;
    color:transparent;
}

 

rule

The selector appears, followed by the declaration block, and the following is a set of rules

.vocabulary{
    height:99px;
    color:transparent;
}

 

Selector

Class selectors like .vocabulary
id selector like #vocabulary
Attribute selector, such as [title='css-world']
Pseudo-class selector, such as: first-child
Pseudo-element selectors like ::before