var totalGifs = 4
var num = (Math.floor(Math.random() * totalGifs) + 1)

supportImageReplacement = false;
browser = navigator.appName;
browser_version = navigator.appVersion;

var isMac = (browser_version.indexOf('Mac') != -1);
var isWindows = ((browser_version.indexOf('Win95') != -1) || (browser_version.indexOf('WinNT') != -1) || (browser_version.indexOf('Win98') != -1))
isNavigator = (browser.indexOf('Netscape') != -1);
isIE = (browser.indexOf('Microsoft Internet Explorer') != -1);

isIE4 = (isIE && (browser_version.indexOf(4.0) != -1));
isIE3 = (isIE && (browser_version.indexOf(3.0) != -1));

isNetscape4 = (isNavigator && (browser_version.indexOf(4.0) != -1));
isNetscape3 = (isNavigator && (browser_version.indexOf(3.0) != -1));

if (isNavigator || isIE4) {
 supportImageReplacement = true;
}

if ((isNetscape3) && (isWindows)) {
 document.write('<img src="images/' + num + 'a.jpg" width="134" height="216" alt="ALT Mask">');
}
else {
 document.write('<img src="images/' + num + 'a.jpg" width="134" height="216" alt="ALT Mask">');
}