CSS positioning techniques

This article explores 6 commonly used properties of CSS. Everyone will be satisfied with this article.

1.position:static

The static attribute is the default value of position, that is, when an element does not have a position attribute set for it, Its default 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 position where the position attribute is not defined. Move down 100px. 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 partial production of fixed patterns, 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 a 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 absolutely positioned based on the element whose external positioning is relative.

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 change. The child element is ""expanded" according to the size of the child element, 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 clear float for the parent element. The sample code is as follows:

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

The above is about learning about the six properties commonly used in CSS positioning. I hope it will be helpful to everyone.

For more articles related to CSS positioning techniques, please pay attention to the PHP Chinese website