Some key points in using the position positioning property of CSS

1.position:static

The static attribute is the default value of position. That is to say, when an element does not have a position attribute set for it, its default value is The value is static.

2.position:absolute
This is a frequently used position attribute value. If absolute is set for an element, the element is separated from the original document flow. To put it more graphically, for example, if the a element is defined with position:absolute, then this element will not have a positional relationship with other elements on the page, but will float above the entire page. Changes in position, size, etc. of other elements on the page will not affect the position of the a element, which is equivalent to an outsider.

3.position:relative
relative is the most useful definition method. Setting the relative attribute indicates the change of the element relative to its original position. For example, we define a b element and set the following css style to it:

#b{     
    position: relative;     
    width:100px;     
    height:100px;     
    top:100px;     
}

The b element defined by this code is positioned relative to the undefined position The attribute's position is moved 100px downward. The definition of the relative attribute value is such a positioning mode.

4.position:fixed
fixed positioning is not used much, but it is very suitable for part of the fixed mode, such as the top menu. After defining the fixed attribute, the position of the element will not change with any behavior.

5.relative+position
Using these two positions at the same time is a very common technique, and novices may also encounter a lot of trouble here. Generally speaking, if an element is absolutely positioned, its reference is based on whether the element closest to itself is set to relative positioning. If there is a setting, it will be positioned as the element closest to itself. If not, it will look to its ancestor elements for relatively positioned elements. Until html is found. For example, the following code uses the combination of the two to implement a two-column layout;

#p-1
 {     
             position:relative;     
}     
            #p-1a
 {     
             position:absolute;     
             top:0;     
             rightright:0;     
             width:200px;     
}     
            #p-1b 
{     
             position:absolute;     
             top:0;     
             left:0;     
             width:200px;     
 }

#The two internal sub-p's will be based on the element whose external positioning is relative. Absolute positioning.

6.clear:both clear float
Sometimes the positioning will collapse, that is, the child element is in the parent element, but the size of the parent element will not follow the child element The size of the element is ""expanded", resulting in the collapse effect of the parent element. This bug occurs because the child element sets the float attribute, causing the parent element to collapse. To solve this bug, you need to set the parent element to the parent element. Set clear float. The sample code is as follows:

#p-1a 
{     
             float:left;     
             width:190px;     
 }     
            #p-1b
 {     
             float:left;     
             width:190px;     
 }     
            #p-1c
 {     
             clear:both;     
 }

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