var browser = '';
var version = '';
var entrance = '';

if (browser == '') {
  if (navigator.appName.indexOf('Microsoft') != -1)
    browser = 'IE'
  else if (navigator.appName.indexOf('Netscape') != -1)
    browser = 'Netscape'
  else browser = 'NN';
}

if (version == '') {
  version = navigator.appVersion;
  paren = version.indexOf('(');
  wholeversion = navigator.appVersion.substring(0,paren-1);
  version = parseInt(wholeversion);
}

if (browser == 'IE' && version >= 4) entrance = 'yes';
if (browser == 'IE' && version < 4) entrance = 'no';
if (browser == 'Netscape' && version >= 2.02) entrance = 'yes';
if (browser == 'Netscape' && version < 2.02) entrance = 'no';

if (entrance == 'yes') {
  button1 = new Image;
  button1.src = "gfx/gbk1.gif";
  button2 = new Image;
  button2.src = "gfx/gbk2.gif";
  button3 = new Image;
  button3.src = "gfx/gbk3.gif";
}

function mouseout(imgName) {
  if (entrance == 'yes') {
    imgout = eval(imgName + '1.src');
    document[imgName].src = imgout;
  }
}

function mouseover(imgName) {
  if (entrance == 'yes') {
    imgover = eval(imgName + '2.src');
    document[imgName].src = imgover;
  }
}

function mousedown(imgName) {
  if (entrance == 'yes') {
    imgdown = eval(imgName + '3.src');
    document[imgName].src = imgdown;
  }
}