DIV的CSS位置（相对位置的绝对值）

Question

In class we learned that if I have two divs: a wrapper div (let's call it div A ) that's defined as position: relative; and another div, div B that's inside div A with position: absolute; .

What will happen is that now the position of div B is dependent on the position of div A . Meaning that now the point 0,0 of div B is not the point 0,0 of the browser, but of div A . So, if I was to move div A say 20 pixels to the right, and div B 30 pixels to the right, div B would be 50 pixels to the right of the browser's point 0,0;

Now, my question is: what if I have 3 divs. Div A that's position: relative; , within it div B that's position: absolute , and within div B , another div (div C ) with position: absolute; . Now, how will div C behave? Will its position 0,0 be that of div A or div B ?

Thanks in advance.

code:

<style type = "text/css">
#a {
position: relative;
left: 20px;
}

#b {
position:absolute;
left: 20px
}

#c {
left: 20px
position:absolute;
}
</style>
<div id = "a">
    <div id = "b">
        <div id = "c">
        test
        </div>
    </div>
</div>

Answer 1

从该JSFiddle中可以看到，“ C” div的位置相对于其父“ B”具有

position: absolute;

Answer 2

I don't have much to add to both these great answers, but here's an article that helped me understand the concept. http://alistapart.com/article/css-positioning-101

EDIT:

That article covers that a div with position absolute is positioned on the inner grid of its closest ancestor(parent, grandparent, etc.) that is fixed, relative, or absolute. If there is none it is relative to the html document, but note it still behaves differently than fixed. It also covers the key differences between the three position types as well as the static position type.

static - this is the default position it creates no grids for children absolute positioned divs. You can't use the css properties top left right or bottom .

relative - creates a grid for descendent(children, grandchildren, etc.) absolute positioned divs. You can use top, left, right and bottom, but they move it 'relative' to where it was previously at. When using top, left, right, and bottom other elements still go around where it was previously at.

absolute - creates a grid for descendent(children, grandchildren, etc.) absolute positioned divs. You can use top, left, right and bottom, but they move it relative to the closest ancestor(parent, grandparent, etc.) grid. Remember the grids are created by fixed, absolute, and relative elements. When using top, left, right, and bottom the element goes out of the flow of the document. (this means other items go through it.)

fixed - creates a grid for children absolute positioned divs. You can use top, left, right and bottom but they move it relative to the browser. When using top, left, right and bottom goes out of the flow of the document. (this means other items go through it.)

Answer 3

Div B-任何绝对定位的元素都根据其最接近的位置（绝对，相对或固定）parent定位 。

Answer 4

这是个人喜好问题，但是与AListApart相比，这篇文章为我带来的好处更多： http ://learnlayout.com/position.html