
        var button_prefix = 'button_';
        
        /**
        * Returns an element in the current HTML document.
        *
        * @param elementID Identifier of HTML element
        * @return               HTML element object
        */
        function getElementObject(elementID) {
            var elemObj = null;
            if (document.getElementById) {
                elemObj = document.getElementById(elementID);
            }
            return elemObj;
        }
        
        /**
        