var bgc = new Array();
bgc[0] = "url(top_20090921/top_090921_1.jpg)";
bgc[1] = "url(top_20090921/top_090921_7.jpg)";
bgc[2] = "url(top_20100111/top_100111_5.jpg)";
bgc[3] = "url(top_20100425/top_100425_5.jpg)";
bgc[4] = "url(top_20100425/top_100425_6.jpg)";
bgc[5] = "url(top_20100425/top_100425_7.jpg)";
bgc[6] = "url(top_20100721/top_100721_1.jpg)";
bgc[7] = "url(top_20100721/top_100721_2.jpg)";
bgc[8] = "url(top_20100721/top_100721_3.jpg)";
n = Math.floor(Math.random()*bgc.length);
document.body.style.backgroundImage = bgc[n]