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1. The float:left element allows any element to be displayed on its right side, whether inline or as a block element. But the left side of it is still not allowed to have any elements with the display, even if the other elements of the code before, unless also to the previous element plus float:left, only allow peers to display.
The Display:inline element is set to allow other inline elements to appear before and after it exists. As for the code in front of the block elements of the display, you want to let the previous element float (whether left or right floating) or set to Display:inline, and the code is behind the block element (whether it is floating, is left floating or right floating), can not be accompanied by, unless set to display: Inline
In addition, the block-level elements are set up display:inline is to solve the famous IE6 double floating weapon.
2.float enables block-level elements to become inline elements!
3,. The row element only left and right margin, no upper and lower margins, and left and right margins will not be merged! Margin merging is only possible with the vertical margin of the block box in the normal document flow. Margins between inline boxes, floating boxes, or absolute positioning are not merged.
4.IE6 The difference between box understanding causes the div set to float to double the value of margin in IE (block-level element margin doubles, and float direction and margin are in the same direction), such as:
 #box {float:left; width:100px; margin:0 0 0 50px; }

//In this case, IE will produce 100px distance
Here's how to fix it:
#box {float:left; width:100px; margin:0 0 0 50px; Display:inline;}
/////Simply add the Display:inline attribute so that floating is ignored, you can resolve

5.
The sum of the width of the float element is less than 100%
6. Float element Be sure to specify the Width property
Many browsers have bugs when displaying a float element that does not have a width specified. So regardless of the contents of the float element, be sure to specify the width property for it.
When specifying an element, use EM instead of PX as a unit.
7. Float element cannot specify attributes such as margin and padding
IE has a bug when displaying float elements that specify margin and padding. Therefore, do not specify the margin and padding properties on the float element (you can nest a div inside a float element to set margin and padding). You can also use the Hack method to specify special values for IE.