var dom = document.getElementById ? true:false;
	var nn4 = navigator.appName=="Netscape" && navigator.appVersion.substring(0,1)=="4" ? true:false;
	var ie4 = document.all ? true:false;

function chgImage(name,state) {
	eval("document."+name+".src='_img/nav/"+name+"_"+state+".gif'");
}
function chgFRImage(layer,name,state) {
	if(nn4)
		eval("document."+layer+".document."+name+".src='_img/nav/"+name+"_"+state+".gif'");
	else
		eval("document."+name+".src='_img/nav/"+name+"_"+state+".gif'");
}

function calcResult() {
	var plus=0;
	var minus=0;
	for(var i=0;i<7;i++) {
		val=document.calc.elements[i].value;
		if(!isNaN(val))
			plus=plus+Number(val);
		else
			document.calc.elements[i].value=0;			
	}
	document.calc.elements[7].value=plus;
	for(var i=8;i<26;i++) {
		val=document.calc.elements[i].value;
		if(!isNaN(Number(val)))
			minus=minus+Number(val);
		else
			document.calc.elements[i].value=0;
	}	
	document.calc.elements[26].value=minus;		
	document.calc.elements[27].value=plus-minus;	
}