css chamfered corner
div {
background: #c00;
/* fallback */
background: -moz-linear-gradient(45deg, transparent 10px, #c00 10px), -moz-linear-gradient(135deg, transparent 10px, #c00 10px), -moz-linear-gradient(225deg, transparent 10px, #c00 10px), -moz-linear-gradient(315deg, transparent 10px, #c00 10px);
background: -o-linear-gradient(45deg, transparent 10px, #c00 10px), -o-linear-gradient(135deg, transparent 10px, #c00 10px), -o-linear-gradient(225deg, transparent 10px, #c00 10px), -o-linear-gradient(315deg, transparent 10px, #c00 10px);
background: -webkit-linear-gradient(45deg, transparent 10px, #c00 10px), -webkit-linear-gradient(135deg, transparent 10px, #c00 10px), -webkit-linear-gradient(225deg, transparent 10px, #c00 10px), -webkit-linear-gradient(315deg, transparent 10px, #c00 10px);
}
div {
background-position: bottom left, bottom right, top right, top left;
-moz-background-size: 50% 50%;
-webkit-background-size: 50% 50%;
background-size: 50% 50%;
background-repeat: no-repeat;
}
/* Ignore the CSS from this point, it's just to make the demo more presentable */
div {
float: left;
width: 50px;
margin: 15px auto;
padding: 15px;
color: white;
line-height: 1.5;
}