inset shadow for "zigzag" border - html

Question

I'm currently designing a website, and for the footer I've created a "zigzag" border on top.
To create some depth in the website, I wanted to add a drop shadow on the triangles in the "zigzag", and this is where I'm currently stuck.
Here is an example of the footer as I have it right now: http://jsfiddle.net/CwXp4/
body {
background: url(http://i.imgur.com/R1yaNOy.png);
}
#footer {
position: absolute;
width: 100%;
height: 200px;
bottom: 0;
background-color: #333;
}
#footer:before {
content: "";
display: block;
position: relative;
top: -21px;
height: 21px;
background: linear-gradient( 45deg, #333 50%, transparent 50%) 0 0, linear-gradient(-45deg, #333 50%, transparent 50%) 0 0;
background-repeat: repeat-x;
background-size: 40px 40px, 40px 40px;
}
<div id="footer"></div>
Is there someone out there with some tips for me on how to add a drop shadow?

Answer 1

You can somehow make the shadow with the same gradients that you are using to make the zigzag.
CSS
#footer:before {
content: "";
display: block;
position: relative;
top: -21px;
height: 22px;
background: linear-gradient( 45deg, #333 50%, blue 50%, transparent 55%) 0 0,
linear-gradient(-45deg, #333 50%, blue 50%, transparent 55%) 0 0;
background-repeat: repeat-x;
background-size: 40px 47px, 40px 47px;
}
body {
background: url(http://i.imgur.com/R1yaNOy.png);
}
#footer {
position: absolute;
width: 100%;
height: 200px;
bottom: 0;
background-color: #333;
}
#footer:before {
content: "";
display: block;
position: relative;
top: -21px;
height: 22px;
background: linear-gradient( 45deg, #333 50%, blue 50%, transparent 55%) 0 0, linear-gradient(-45deg, #333 50%, blue 50%, transparent 55%) 0 0;
background-repeat: repeat-x;
background-size: 40px 47px, 40px 47px;
}
<div id="footer"></div>
fiddle
You could also get the shadow with a webkit-filter shadow, but this has limited support
CSS
#footer:before {
content: "";
display: block;
position: relative;
top: -21px;
height: 22px;
background: linear-gradient( 45deg, #333 50%, transparent 50%) 0 0,
linear-gradient(-45deg, #333 50%, transparent 50%) 0 0;
background-repeat: repeat-x;
background-size: 40px 47px, 40px 47px;
-webkit-filter: drop-shadow(red 0px -5px 5px);
}
body {
background: url(http://i.imgur.com/R1yaNOy.png);
}
#footer {
position: absolute;
width: 100%;
height: 200px;
bottom: 0;
background-color: #333;
}
#footer:before {
content: "";
display: block;
position: relative;
top: -21px;
height: 22px;
background: linear-gradient( 45deg, #333 50%, transparent 50%) 0 0, linear-gradient(-45deg, #333 50%, transparent 50%) 0 0;
background-repeat: repeat-x;
background-size: 40px 47px, 40px 47px;
-webkit-filter: drop-shadow(red 0px -5px 5px);
}
<div id="footer"></div>
fiddle with filter