It's because of x and y offset. Try this:

-webkit-box-shadow: 0 0 10px #fff;
box-shadow: 0 0 10px #fff;

edit (year later..): Made the answer more cross-browser, as requested in comments :)

btw: there are many css3 generator nowadays.. css3.me, css3maker, css3generator etc...

See: http://jsfiddle.net/thirtydot/cMNX2/8/

input {
-webkit-box-shadow: 0 0 5px 2px #fff;
-moz-box-shadow: 0 0 5px 2px #fff;
box-shadow: 0 0 5px 2px #fff;
}

This looks cool.

-moz-box-shadow: 0 0 5px #999;
-webkit-box-shadow: 0 0 5px #999;
box-shadow: 0 0 5px #999;

I found the http://css-tricks.com/forums/topic/how-to-add-shadows-on-all-4-sides-of-a-block-with-css/ site.

.allSides
{
width:350px;height:200px;
border: solid 1px #555;
background-color: #eed;
box-shadow: 0 0 10px rgba(0,0,0,0.6);
-moz-box-shadow: 0 0 10px rgba(0,0,0,0.6);
-webkit-box-shadow: 0 0 10px rgba(0,0,0,0.6);
-o-box-shadow: 0 0 10px rgba(0,0,0,0.6);
}

Just simple as this code:

box-shadow: 0px 0px 2px 2px black; /*any color you want*/

Use this css code for all four sides: box-shadow: 0px 1px 7px 0px rgb(106, 111, 109);

The most simple solution and easiest way is to add shadow for all four side. CSS

box-shadow: 0 0 2px 2px #ccc; /* with blur shadow*/
box-shadow: 0 0 0 2px #ccc; /* without blur shadow*/

You can different combinations at the following link.
https://www.cssmatic.com/box-shadow

The results which you need can be achieved by the following CSS

-webkit-box-shadow: 0px 0px 11px 1px rgba(0,0,0,1);
-moz-box-shadow: 0px 0px 11px 1px rgba(0,0,0,1);
box-shadow: 0px 0px 11px 1px rgba(0,0,0,1);

Understand box-shadow syntax and write it accordingly

box-shadow: h-offset v-offset blur spread color;

h-offset: Horizontal offset of the shadow. A positive value puts the shadow on the right side of the box, a negative value puts the shadow on the left side of the box - Required

v-offset: Vertical offset of the shadow. A positive value puts the shadow below the box, a negative value puts the shadow above the box - Required

blur: Blur radius (The higher the number, the more blurred the shadow will be) - Optional

color: Color of the shadow - Optional

spread: Spread radius. A positive value increases the size of the shadow, a negative value decreases the size of the shadow - Optional

inset: Changes the shadow from an outer shadow to an inner shadow - Optional

box-shadow: 0 0 10px #999;

box-shadow works better with spread

box-shadow: 0 0 10px 8px #999;

use 'inset' to apply shadow inside of the box

box-shadow: 0 0 8px inset #999;
(or)
box-shadow: 0 0 8px 8px inset #999;

use rgba (red green blue alpha) to adjust the shadow more efficiently

box-shadow: 0 0 8px inset rgba(153, 153, 153, 0.8);
(or)
box-shadow: 0 0 8px 8px inset rgba(153, 153, 153, 0.8);

CSS3 box-shadow: 4 sides symmetry

1. each side with the same color

:root{
--color: #f0f;
}


div {
display: flex;
flex-flow: row nowrap;
align-items: center;
justify-content: center;
box-sizing: border-box;
margin: 50px auto;
width: 200px;
height: 100px;
background: #ccc;
}


.four-sides-with-same-color {
box-shadow: 0px 0px 10px 5px var(--color);
}

<div class="four-sides-with-same-color"></div>

2. each side with a different color

:root{
--color1: #00ff4e;
--color2: #ff004e;
--color3: #b716e6;
--color4: #FF5722;
}


div {
display: flex;
flex-flow: row nowrap;
align-items: center;
justify-content: center;
box-sizing: border-box;
margin: 50px auto;
width: 200px;
height: 100px;
background-color: rgba(255,255,0,0.7);
}


.four-sides-with-different-color {
box-shadow:
10px 0px 5px 0px var(--color1),
0px 10px 5px 0px var(--color2),
-10px 0px 5px 0px var(--color3),
0px -10px 5px 0px var(--color4);
}

<div class="four-sides-with-different-color"></div>

screenshots

refs

https://css-tricks.com/almanac/properties/b/box-shadow/

https://www.cnblogs.com/xgqfrms/p/13264347.html

Using (v1)px (v2)px (v3)px (v4)px as an example. v1px when positive gives right side shadow whiles negative value gives left side shadow. v2px when positive gives top side shadow whiles negative value gives bottom side shadow. v3 is used for making the shadow blur. 10px will make shadow more blur than 5px and so on So using a div (mydiv) with style below. We will get the image below

box-shadow:
30px 0px 5px 0px red,
0px 30px 5px 0px blue,
-30px 0px 5px 0px green,
0px -30px 5px 0px yellow;
width:200px;
height:200px;
margin-left:100px;
}


<br><br>


<div class="mydiv"></div>


This should give you the div below
view the result from this link: https://i.stack.imgur.com/bUjRN.jpg

Add this line to your box style.

box-shadow: 0 0 0 width color;

as example:

box-shadow: 0 0 0 5px yellow;

You can find more details here MDN Web Docs - Setting zero for offset and blur

Make the x and y offsets negative to apply the shadows on left and top sides of the container as well.

div { box-shadow: 1px 1px 1px 1px #BDBDBD, -1px -1px 1px 1px #BDBDBD; }

In the above code block,

1. 1px 1px 1px 1px #BDBDBD is for adding shadows to the right and bottom sides.
2. -1px -1px 1px 1px #BDBDBD is for adding shadows to the top and left sides.

Just simple as this:

box-shadow: 3px 3px 5px rgb(186 195 78), -3px -3px 5px rgb(186 195 78);

box-shadow: 0px 0px 4px 4px #000;

Where:

• The first 2 values are the offset-x and offset-y of the shadow
• The 3rd value - blur radius
• The 4th value - spread radius

Else, you can generate a box-shadow online, using CSS box shadow generator