function showgraph( id, x, y ) {
  y_off = (document.all) ? document.documentElement.scrollTop : window.pageYOffset;
  x_off = (document.all) ? document.documentElement.scrollLeft : window.pageXOffset;
  document.getElementById( id ).style.top = ( y_off + y ) + 'px';
  document.getElementById( id ).style.left = ( x_off + x + 20 ) + 'px';
  document.getElementById( id ).style.display = 'block';
}

function hidegraph( id ) {
  document.getElementById( id ).style.display = 'none';
}