/*------------------------------------*\
	BORDERS
\*------------------------------------*/

/* Create a series of empty pseudo-elements... */
html:before,html:after,body:before,body:after{
	content:"";
	background:#dad8bb;
	position:fixed;
	display:block;
	z-index:5;
}

/* ...and position them! */
html:before{
	height:10px;
	left:0;
	right:0;
	top:0;
}
html:after{
	width:10px;
	top:0;
	right:0;
	bottom:0;
}
body:before{
	height:10px;
	right:0;
	bottom:0;
	left:0;
}
body:after{
	width:10px;
	top:0;
	bottom:0;
	left:0;
}

http://csswizardry.com/2010/12/simplified-page-borders-in-pure-css/

Inserire bordi alla pagina tramite CSS

Page borders in pure CSS

css, body

CSS