inset-border.css

/*All you have to do is create a div inside the div you want to give an inset border to*/

#something {
    background: transparent url(http://davidrhysthomas.co.uk/linked/astrid_avatar.png) 50% 50% no-repeat;
    min-width: 300px;
    min-height: 300px;
    padding: 0;
    position: relative;
}

#something div {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    border: 10px solid rgba(0,255,0,0.6);
}