var loadImg = new Array(
	'images/bt_about_ov.gif',
	'images/bt_company_ov.gif',
	'images/bt_recruit_ov.gif',
	'images/bt_qa_ov.gif'
);
var PrImg = new Array();
for(i=0; i<loadImg.length; i++){
	PrImg[i] = new Image();
	PrImg[i].src = loadImg[i];
}
var mainNum = 1;
var num;
var img;
function ovImg(num) {
		imageChange(num);
		var changePict = "changePict" + num;
		changePict = document.getElementById(changePict);
		changePict.src = "./images/"+ img + "ov.gif";
	}
function offImg(num) {
		imageChange(num);
		var changePict = "changePict" + num;
		changePict = document.getElementById(changePict);
		var baseNode = document.getElementById("head");
		changePict.src = "./images/"+ img + "off.gif";
		if( baseNode.className == "index" ){
			var changePict1 = document.getElementById("changePict1");
			changePict1.src = "./images/bt_about_ov.gif";
		}
		else if( baseNode.className == "company" ){
			var changePict2 = document.getElementById("changePict2");
			changePict2.src = "./images/bt_company_ov.gif";
		}
		else if( baseNode.className == "recruit" ){
			var changePict3 = document.getElementById("changePict3");
			changePict3.src = "./images/bt_recruit_ov.gif";
		}
		else if( baseNode.className == "qanda" ){
			var changePict4 = document.getElementById("changePict4");
			changePict4.src = "./images/bt_qa_ov.gif";
		}
	}
function imageChange(num){
	if( num == 1 ){
		img = "bt_about_"
	}
	else if( num == 2 ){
		img = "bt_company_"
	}
	else if( num == 3 ){
		img = "bt_recruit_"
	}
	else if( num == 4 ){
		img = "bt_qa_"
	}
}