CSS3盒子阴影: 插图可以只做一边或两边吗? 像边框顶部？

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box-shadow is for all four sides. You can't change that (yet?). The 4 sizes in the box-shadow definition are OffsetX, offsetY, Blur and Spread.

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No, not directly, but you can crop off the parts that you don't want by putting it in a div with overflow: hidden:

http://jsfiddle.net/Vehdg/

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I don't think your really need box-shadow-top because if you set offsetx to 0 and offsety to any positive value only remaining shadow is on top.

if you want to have shadow on top and shadow in the bottom you just can simply use two divs:

<div style="box-shadow:inset 0 1px 5px black;">
<div style="box-shadow:inset 0 -1px 5px black;">
some content
</div>
</div>

if you want to get rid of shadow on sides use rgba instead of hex color and set bigger offsety:

box-shadow:inset 0 5px 5px rgba(0,0,0,.5)

this way you give shadow more opacity so sides stay hidden and with more offset you get less opacity

full example:

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<style type="text/css">
body {
background: #1C1C1C;
}
div {
margin: 50px auto;
width: 200px;
height: 200px;
background: #fff;
-webkit-border-radius: 20px;
-khtml-border-radiust: 20px;
-moz-border-radius: 20px;
-o-border-radius: 20px;
border-radius: 20px;
box-shadow:inset 0px 5px 5px rgba(0,0,0,.5);
}
div > div {
background:none;
box-shadow:inset 0px -5px 5px rgba(0,0,0,.5);
}
</style>
</head>
<body>
<div><div></div></div>
</body>
</html>

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using :before and after elements with regular shadows cut of by overflow:hidden on the parent box like in this example: http://dabblet.com/gist/2585782

CSS

/**
* Top and Bottom inset shadow
*/




#element{
background-color: #E3F2F7;
height: 55px;
position: relative; /* to position pseudo absolute*/
overflow: hidden; /* to cut of overflow shadow*/
margin-top: 200px;
}


#element:before , #element:after{
content: "\0020";
display: block;
position: absolute;
width: 100%;
height: 1px; /* when 0 no shadow is displayed*/
box-shadow: #696c5c 0 0 8px 0;
}


#element:before { top: -1px} /* because of height: 1*/
#element:after { bottom: -1px}  /* because of height: 1*/

HTML

<div id="element"></div>

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You can use a background gradient for a work around in most cases:

SCSS(with compass) example:

@include background(linear-gradient(top, #666 1%, #999 3%, #ddd 6%, #f6f6f6 9%, #f6f6f6 92%, #ddd 94%, #999 97%, #666 99%) );

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最佳答案

This is what worked for me:

box-shadow: inset 1px 4px 9px -6px;

Example: http://jsfiddle.net/23Egu/

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You can accomplish a single-sided, inner shadow by setting your div to overflow:hidden and adding shadow elements along the borders.

Set an inner shadow on the top and bottom borders of a division:

HTML

<div id="innerShadow">
<div id="innerShadowTop">
Content...
<div id="innerShadowBottom">
</div>

CSS

#innerShadow
{
position: relative;
overflow: hidden;
}


#innerShadowTop
{
width: 100%;
height: 1px;
margin: 0;
padding: 0;
position: absolute;
top: -1px;
-moz-box-shadow: 0px 1px 6px 1px rgba(0, 0, 0, 0.65);
-webkit-box-shadow: 0px 1px 6px 1px rgba(0, 0, 0, 0.65);
-o-box-shadow: 0px 1px 6px 1px rgba(0, 0, 0, 0.65);
box-shadow: 0px 1px 6px 1px rgba(0, 0, 0, 0.65);
}


#bannerShadowBottom
{
width: 100%;
height: 1px;
margin: 0;
padding: 0;
position: absolute;
bottom: -1px;
-moz-box-shadow: 0px -1px 6px 1px rgba(0, 0, 0, 0.65);
-webkit-box-shadow: 0px -1px 6px 1px rgba(0, 0, 0, 0.65);
-o-box-shadow: 0px -1px 6px 1px rgba(0, 0, 0, 0.65);
box-shadow: 0px -1px 6px 1px rgba(0, 0, 0, 0.65);
}

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box-shadow: inset 5px 0 5px -5px rgba(0,0,0,0.5),inset -5px 0 5px -5px rgba(0,0,0,0.5);
-moz-box-shadow: inset 5px 0 5px -5px rgba(0,0,0,0.5),inset -5px 0 5px -5px rgba(0,0,0,0.5);
-webkit-box-shadow: inset 5px 0 5px -5px rgba(0,0,0,0.5),inset -5px 0 5px -5px rgba(0,0,0,0.5);
-o-box-shadow: inset 5px 0 5px -5px rgba(0,0,0,0.5),inset -5px 0 5px -5px rgba(0,0,0,0.5);

This works just lovely :)

Here is a codepen illustrating it: http://codepen.io/poopsplat/pen/cGBLy

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Multiple box shadows did the trick for me.

box-shadow:
inset 0 -8px 4px 4px rgb(255,255,255),
inset 0 2px 4px 0px rgba(50, 50, 50, 0.75);

http://jsfiddle.net/kk66f/

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For the same shadow but only on the top :

box-shadow: inset 0px 6px 5px -5px black;

To have the shadow in one direction you have to negate the "blur" parameter with the "spread" parameter and then adjust the "h-pos" and/or "v-pos" parameters by this same value. It doesn't work with opposite border or triple border. You have to add one more definition.

More examples here : http://codepen.io/GBMan/pen/rVXgqP

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I just had this problem myself. The solution that I found was with multiple box-shadows (one for each side that you want your shadow). Here is the definition:

box-shadow: none|h-offset v-offset blur spread color |inset|initial|inherit;

Here is how to think it:

first, make the spread 0 (this will disable the effect on all sides)
the h-offset (if you set it to be positive, it will cast on the left side, if you set it negative, on the right side)
the v-offset (if you set it to be positive, it will cast on the top side, if you set it negative, on the bottom side

Here you can see my case with box-shadow on three sides (left, top, right and the bottom is with same color as the background to create the effect that I wanted - the left side and the right go all the way to the bottom) https://codepen.io/cponofrei/pen/eMMyQX