if (document.images) {

var navi_1 = new Image()
navi_1.src = "common/images/top_btn_off.jpg";
var navi_1_2 = new Image()
navi_1_2.src = "common/images/top_btn_on.jpg";

var navi_2 = new Image()
navi_2.src = "common/images/works_btn_off.jpg";
var navi_2_2 = new Image()
navi_2_2.src = "common/images/works_btn_on.jpg";

var navi_3 = new Image()
navi_3.src = "common/images/company_btn_off.jpg";
var navi_3_2 = new Image()
navi_3_2.src = "common/images/company_btn_on.jpg";

var navi_4 = new Image()
navi_4.src = "common/images/contact_btn_off.jpg";
var navi_4_2 = new Image()
navi_4_2.src = "common/images/contact_btn_on.jpg";

}

function act(imgName) {
	if (document.images)
	document[imgName].src = eval(imgName + '_2.src')
}

function inact(imgName) {
	if (document.images)
	document[imgName].src = eval(imgName + '.src')
}