var azar = parseInt((Math.round((Math.random() * 1))));;
url_htmls = new Array();
url_img = new Array();

url_htmls[0] = 'http://www.chicasenvideochat.com/';
url_htmls[1] = 'http://www.chicasenvideochat.com/';

url_img[0] = 'http://descargas2.tuvideogratis.com/todocvcd/banners2/120x600_03.gif';
url_img[1] = 'http://descargas2.tuvideogratis.com/todocvcd/banners2/120x600_04.gif';

var banner = '';
banner += '<' + 'a href="' + url_htmls[azar] + '" target="_blank"><' + 'img src="' + url_img[azar] + '" ';
banner += ' width="120" height="600" border="0"><' + '/a>'; 

document.write(banner);