function getInternetExplorerVersion()
// Returns the version of Internet Explorer or a -1
// (indicating the use of another browser).
{
	var rv = -1; // Return value assumes failure.
	if (navigator.appName == 'Microsoft Internet Explorer')
	{
		var ua = navigator.userAgent;
		var re  = new RegExp("MSIE ([0-9]{1,}[\.0-9]{0,})");
		if (re.exec(ua) != null)
			rv = parseFloat( RegExp.$1 );
	}
	return rv;
}