Absolute positioning

Absolute positioning

             Absolute positioning 
                 - When the element of position Property value set to absolute when , The absolute positioning of elements is turned on 
                 - The characteristics of absolute positioning ：
                        1. After turning on absolute positioning , If you don't set the offset, the position of the element doesn't change 
                        2. After turning on absolute positioning , The element is detached from the document stream 
                        3. Absolute positioning changes the nature of the element , It's a block in the industry , The width and height of the block are spread by the content 
                        4. Absolute positioning will raise the element to a higher level 
                        5. Absolute positioning elements are positioned relative to their containing blocks 

                 Containing block （containing block）：
                      - Under normal circumstances ：
                            The containing block is the closest ancestor block element to the current element 
                      - Absolutely positioned containing blocks ：
                            - The containing block is the nearest ancestor element that opens the location 
                                  If all ancestor elements have not enabled positioning, positioning relative to the root element is its containing block 
                        -html（ Root element 、 Initial inclusion block ）