CSS:
#box {
width: 200px;
height: 200px;
background: black;
position: relative;
-webkit-transition: all 300ms ease-in;
}
#box:hover {
-webkit-transform: rotate(-180deg) scale(0.8);
}
#box:after, #box:before {
display: block;
content: "\0020";
color: transparent;
width: 211px;
height: 45px;
background: white;
position: absolute;
left: 1px;
bottom: -20px;
-webkit-transform: rotate(-12deg);
-moz-transform: rotate(-12deg);
}
#box:before {
bottom: auto;
top: -20px;
-webkit-transform: rotate(12deg);
-moz-transform: rotate(12deg);
}
HTML:
<div id=box></div>
Works in Chrome and FF 4: http://jsfiddle.net/rudiedirkx/349x9/
This might help: http://jsfiddle.net/rudiedirkx/349x9/2880/
And this too (from Erwinus' comment): http://css-tricks.com/examples/ShapesOfCSS/