function browser_name() {
		var browser_name = navigator.appName;
		return browser_name;
	}

	function browser_version() {
		var browser_version = parseFloat(navigator.appVersion);
		return browser_version;
	}

	function browser_os() {
		if(navigator.appVersion.indexOf("Win95") > 0) return "WIN95";
		else if(navigator.appVersion.indexOf("Win16") > 0) return "WIN31";
		else if(navigator.appVersion.indexOf("WinNT") > 0) return "NT";
		else if(navigator.appVersion.indexOf("Mac") > 0) return "MAC";
		else if(navigator.appVersion.indexOf("UNIX") > 0) return "UNIX";
		else return "UNKNOWN";
	}

var browserOk = false;

if (browser_name() == "Netscape" && browser_version() >= 3.0) browserOk = true;
else if (browser_name() == "Microsoft Internet Explorer" && browser_version() >= 3.0) browserOk = true;

function chg_button(titlename, onoff) 
{

 if (browserOk == true) {
		document[titlename].src = "images/button_" + titlename + "_" + onoff + ".gif"
	}
}