/* global variable */
var seed, old_seed;

// 圖片的 URL 請用絕對路徑
// flash 路徑請用空字串，並請 art 將連結加到 flash 中

var ad_count = 2;
var ad_url = new Array(ad_count);
var ad_img = new Array(ad_count);

ad_url[0] = "http://learnabc.tfn.net.tw/";
ad_img[0] = "images/ad_abc.jpg";

ad_url[1] = "http://www.tfn.net.tw/adsl_plus/va_pcschool/index.asp";
ad_img[1] = "images/ad_computer.jpg";



function showbanner() {
	seed = (Math.round(Math.random() * 100)) % ad_count;
	if (seed == old_seed)
		return;

	if (ad_url[seed].length == 0) {
		if (ad_url[old_seed].length == 0)
			old_seed = seed;
	} else {
		if (ad_url[old_seed].length > 0)
			old_seed = seed;
	}
	if (seed == old_seed)
		document.banner.src = ad_img[seed];
}

function chglink() {
	newWindow = window.open(ad_url[old_seed], "_new");
}

function draw_banner() {
	seed = (Math.round(Math.random() * 100)) % ad_count;
	old_seed = seed;

	if (ad_url[seed].length == 0) {
		document.write('<embed name="banner" src="' + ad_img[seed] + '" pluginspage="http://www.macromedia.com/shockwave/download/" type="application/x-shockwave-flash" width="468" height="60">');
		document.write('</embed>');
	} else {
		// document.write("<img name=banner src=\"" + ad_img[seed] +  "\" width=\"472\" height=\"206\" border=0");
		document.write("<img name=banner src=\"" + ad_img[seed] +  "\" width=\"472\" height=\"206\" border=0 style=\"cursor:hand\" onClick=\"chglink();\"");
	}
};