var imgfold = 'images/';
var loaded  = 0;

function changeImage(ni) {
  var my_img = new Image(0,0);
  my_img.src = ni;
  document['big_placeholder'].src = my_img.src
}

function LoadTabs() {
  tab1_off = new Image(0,0);    tab1_off.src = imgfold + "tab_1_off.gif";
  tab1_on = new Image(0,0);     tab1_on.src  = imgfold + "tab_1_on.gif";

  tab2_off = new Image(0,0);    tab2_off.src = imgfold + "tab_2_off.gif";
  tab2_on = new Image(0,0);     tab2_on.src  = imgfold + "tab_2_on.gif";

  tab3_off = new Image(0,0);    tab3_off.src = imgfold + "tab_3_off.gif";
  tab3_on = new Image(0,0);     tab3_on.src  = imgfold + "tab_3_on.gif";

  tab4_off = new Image(0,0);    tab4_off.src = imgfold + "tab_4_off.gif";
  tab4_on = new Image(0,0);     tab4_on.src  = imgfold + "tab_4_on.gif";

  loaded = "1";
}

function changTab(tabNum) {
  for(i=1; i<=4; i++) {
    deactivate('tab'+i);
  }
  activate('tab'+tabNum);
  loadPage(''+tabNum);
  return false;
}

function activate(imgName) {
  if ( loaded == "1" ) { document[imgName].src = eval(imgName + "_on.src"); }
}
function deactivate(imgName) {
  if ( loaded == "1" ) { document[imgName].src = eval(imgName + "_off.src"); }
}

function loadPage(tabID) {
  frames['tab_content'].location.href = 'tab_' + tabID + '_content.html'
}