Visual Format mode

1. Margin and padding
Margin is the external frame of block elements (such as Div ).
Padding is the inner frame of a block element.
2. Positioning
A. Relative positioning: relative to the position of the previous block element
Position: relative; left: 20px; top: 20px;
B. Absolute positioning: relative position to the parent element (may overwrite other elements)
Position: absolute; left: 20px; top: 20px;
C. Floating: a positional relationship between elements
Float indicates floating, Clear indicates not floating
Float: Left; clear: both;