function select_page (part) {
  if (!part) suffix = "";
   else suffix = part + "_";

  if(document.images) {
    b1 = new Image; b1.src = "/images/b1_" + suffix + ".gif"; 
    b2 = new Image; b2.src = "/images/b2_" + suffix + ".gif"; 
    b3 = new Image; b3.src = "/images/b3_" + suffix + ".gif"; 
    b4 = new Image; b4.src = "/images/b4_" + suffix + ".gif"; 
    b5 = new Image; b5.src = "/images/b5_" + suffix + ".gif"; 
  }

}

function img_on (iName, iPath) {
  document.images[iName].src = iPath;
} 

function img_off (iName, iPath) {
  document.images[iName].src = iPath;
}