/**
	 * Switch the src of the given image (oImg) from either default to on
	 * (sType = 'on') or from on to default (sType = 'default').
	 * The images from which this function is invoked have two additional 
	 * attributes, being 'on' and 'default'. These attributes correspond to
	 * the sType argument given.
	 * 
	 * @author R.J.T. de Vries <rdevries@thirdwave.nl>
	 * @param		object 	oImg		image that invoked this function
	 * @return 	string	sType		type of src to switch to
	 * @access public
	 */
	function switchImg(oLink, sType) {
	
		if ( typeof(oLink) == 'undefined' ) return false;
		
		if ( !oLink.childNodes || !oLink.childNodes.length ) return false;
		
		for ( var i = 0; i < oLink.childNodes.length; i++ ) {

			if ( oLink.childNodes[i].nodeType == 1 && oLink.childNodes[i].tagName
			
					&& oLink.childNodes[i].tagName == 'IMG' ) {
			
				var oImg = oLink.childNodes[i];

			}
		
		} // for()
		
		if ( typeof(oImg) == 'undefined' || !oImg || oImg == 'null' ) return false;
		
		var newsrc = oImg.getAttribute(sType);
		
		if ( typeof(newsrc) == 'undefined' || !newsrc ) return false;
		
		oImg.setAttribute('src', '/graphics/buttons/' + newsrc);
		
		return true;
	
	} // switchImg()