左浮动框
BFC
重置
float
left
right
none
position
relative
absolute
fixed
display
block
inline
inline-block
table-cell
table-caption
flex
overflow
visible
hidden
scroll
auto
左浮动框
重置
float
left
right
none
position
relative
absolute
fixed
display
block
inline
inline-block
table-cell
table-caption
flex
overflow
visible
hidden
scroll
auto
块级盒子1，margin-bottom : 20px
块级盒子2，margin-top : 20px
重置
float
left
right
none
position
relative
absolute
fixed
display
block
inline
inline-block
table-cell
table-caption
flex
overflow
visible
hidden
scroll
auto