Why does the right float after the order is reversed

Why the right float after the order is reversed:

Sometimes you will find a strange phenomenon, that is, to add the right float for the object, the display order and the original order is reversed, the following combination of example distribution analysis of the cause of this phenomenon.

Example one:

<! DOCTYPE html>
 
In the above code, the order of the elements is arranged in code order.
 
Example two:
 
<! DOCTYPE html>
 
Adding a right float to the span element in the code above, the results are arranged in the opposite order of code, which is actually very simple, because the code is executed sequentially, so the first span will be first right floating, then the second span right floats, and so on, so the order will be reversed.
 
The original address is: http://www.51texiao.cn/div_cssjiaocheng/2015/0507/906.html
 
The most original address is: http://www.softwhy.com/forum.php?mod=viewthread&tid=4649
Why does the right float after the order is reversed