Create border with two cut off corners - css

Question

I want to create a border with two cut off corners for my website. I need this border for different div sizes.
After an hour or so I got it to work with a fixed size of 200px. But I don't know how I can get this flexible.
Here's a
Demo
HTML
<div id="outer"><span>Some Text</span></div>
CSS
body {background: #000;}
#outer {
width: 200px;
height: 200px;
position: relative;
margin: 0 auto;
margin-top: 50px;
background: #0ff;
}
#outer:before {
content: "";
height: 200px;
left: -15px;
position: absolute;
border-top: 15px solid transparent;
border-right: 15px solid #fff;
}
#outer:after {
content: "";
width: 200px;
height: 200px;
top: -15px;
right: -215px;
position: absolute;
border-left: 15px solid #fff;
border-bottom: 15px solid transparent;
}
#outer span {
width: 200px;
height: 200px;
position: absolute;
padding: 50px;
}
#outer span:before {
display: block;
content: "";
width: 200px;
top: -15px;
left: 0;
position: absolute;
border-bottom: 15px solid #fff;
border-left: 15px solid transparent;
}
#outer span:after {
display: block;
content: "";
width: 200px;
height: 200px;
top: 200px;
left: -15px;
position: absolute;
border-top: 15px solid #fff;
border-right: 15px solid transparent;
}
Anyone knows a better solution? Thanks

Answer 1

You pretty much have it yourself. I adapted the fiddle to use percent values for the dimensions and positions. It's still 15px wide for the border though:
Demo: http://jsfiddle.net/b48AK/show
Source: http://jsfiddle.net/b48AK
body {background: #8aa; padding:0px; margin:0px}
#outer {
background: #bfb;
position:relative;
margin:15px;
}
#outer:before {
content: "";
height: 100%;
left: -15px;
position: absolute;
border-top: 15px solid transparent;
border-right: 15px solid #fff;
}
#outer:after {
content: "";
width: 100%;
height: 100%;
top: -15px;
left: 100%;
position: absolute;
border-left: 15px solid #fff;
border-bottom: 15px solid transparent;
}
#outer span:before {
display: block;
content: "";
width: 100%;
top: -15px;
left: 0;
position: absolute;
border-bottom: 15px solid #fff;
border-left: 15px solid transparent;
}
#outer span:after {
display: block;
content: "";
width: 100%;
height: 100%;
top: 100%;
left: -15px;
position: absolute;
border-top: 15px solid #fff;
border-right: 15px solid transparent;
}
​