Basic knowledge sharing of div and css layout-JS Tutorial-php.cn

Css and div are both language codes that are inseparable from page layout. This article mainly shares with you the basic knowledge of div and css layout, hoping to help everyone.

1 p+css layout?
Keywords: box position
margin
padding
float
position
What did you learn? Essentially, just learn how to position the box (p)

2 Box model?
width: width
height: height
border: border
margin: outer margin
padding: inner margin
Function: the position used to place the content

2.1 margin outer margin

Rule: border margin padding: four sides (up, down, left and right)
border-left
border-right
border-top
border-bottom

2.2 Simple issues to note about margin:
The body has a default margin: chrome 8px
If the margins of the upper and lower boxes are set, the distance between the two boxes is based on the larger margin (margin collapse)
Center the box: margin: 10px auto;

3 padding inner margin
Function: Used to adjust the placement of the content inside the box
Note: After setting padding, the outer box will be integrated Bigger? Impact: Affects the layout of the entire web page
The total width of the box: 300(width) + padding-left/right(10+10) + border-left/right(5+5) = 330

4 Block-level elements and inline elements
Block-level elements: p h1 p li, etc. If they occupy one line, you can set the width and height
Inline elements: span i a img, etc. When displayed in one line, you generally cannot set the width and height
Convert inline elements to block-level elements: After conversion, width and height can be supported

Rule: p+css layout, margin, padding, float, and position are all related to position. Place the box in the appropriate position

5 float Float

Normal flow: the natural sorting rules of elements when special css rules such as positioning and floating are not used
Floating: out of the normal flow, elements can move left and right
float:left
float:right
Function: Make the left and right layout of the box

Problems caused by floating: It may affect the layout of subsequent elements
Solution: After floating The float must be cleared after the element

float: left and right layout
margin: adjust the distance between boxes
padding
position: positioning fixed position function-you can place the element in any position

6 Relative positioning
postion:relative
Reference object: Who does this positioning according to? Your own initial position before positioning is not used
To change the position, an offset is required Amount
left: 100px
Offset 100px to the right based on the position before positioning is not used

7 Absolute positioning
position:absolute
Reference: 1 In the parent element 2 with positioning attribute and is looking for the nearest parent with positioning attribute
Offset: left top right bottom

The order of finding the reference: first find the parent element, If there is a position attribute (position), the parent element will be used as a reference to offset.
If not found, search the outer layers one by one until an element with a position attribute is found. If there is none, then use the last The outer html
element is offset for the reference object

8 Fixed positioning
Reference object: Browser visible area

9 Exercise

10. Other selectors
Selectors: Methods for selecting elements id ==> # class ==> . Tag selector ==> Tag name

10.1 Adjacent selector ==> + Select elements adjacent to an element

10.2 Multi-element selector ==>, application scenario: there are multiple elements with the same attributes (and many codes are repeated, which can be extracted and made public )

10.3 Descendant selector ==> space, application scenario: select descendant elements that meet the conditions

10.4 Child element selector==> >, application scenario: select those that meet the conditions Conditional sub-elements

Note: Sub-elements can only select elements of the next layer. Descendant selectors can select n-layer elements below
Function: They are all used to conveniently select elements

10.5 Attribute selector ==> Element [Attribute = Attribute value] Application scenario: Select elements with certain attributes
name
name = value
name ^= val
name $= val
Can be understood as filtering conditions

11, pseudo-class, pseudo-element

1 p+css layout?
Keywords: box position
margin
padding
float
position
What are you learning? Essentially, just learn how to position the box (p)

2 Box model?
width: width
height: height
border: border
margin: outer margin
padding: inner margin
Function: the position used to place content