var baseText = null;
function showPopup(id, w, h) {            
    var top = ((document.viewport.getHeight() / 2) + document.viewport.getScrollOffsets().top - (h / 2));
    if (top < 0) top = 0;
    $(id).setStyle({ 'top': top + 'px', 'left': '200px', 'width': w + 'px', 'height': h + 'px' });                                    
    if (baseText == null) {
        baseText = $(id).innerHTML;
        var d = new Draggable(id);
        $(id).insert(new Element('div', { 'class': 'closebar' }).update(new Element('input', { 'type': 'button', 'value': 'Close'})).observe('click', function() { $(id).toggle(); }), {'position': 'after'});
    }
    $(id).toggle();
}