[cc lang=”html”]
.arrow-up {
width: 0;
height: 0;
border-left: 5px solid transparent;
border-right: 5px solid transparent;
border-bottom: 5px solid black;
}
.arrow-down {
width: 0;
height: 0;
border-left: 20px solid transparent;
border-right: 20px solid transparent;
border-top: 20px solid #f00;
}
.arrow-right {
width: 0;
height: 0;
border-top: 60px solid transparent;
border-bottom: 60px solid transparent;
border-left: 60px solid green;
}
.arrow-left {
width: 0;
height: 0;
border-top: 10px solid transparent;
border-bottom: 10px solid transparent;
border-right:10px solid blue;
}
[/cc]
and here are a bunch of other CSS shapes
http://www.cssportal.com/css3-shapes/
or just use this CSS Triangle Generator