docs: function ( anchor, headerHeight, offset ) {
  		var location = 0;
  		if (anchor.offsetParent) {
  			do {
  				location += anchor.offsetTop;
  				anchor = anchor.offsetParent;
  			} while (anchor);
  		}
  		location = location - headerHeight - offset;
  		if ( location >= 0 ) {
  			return location;
  		} else {
  			return 0;
  		}
  	}