theAds = new Array();  

theAds[0] = "<a href=\"http://www.huajungroup.com/msr/\"><img src=../images/468x60_MSR_Banner001.gif border=1 height=62></a>";  
theAds[1] = "<a href=\"http://www.huajungroup.com/msr/msr_products.asp\"><img src=../images/468x60_MSR_Banner002.gif border=1></a>"; 
theAds[2] = "<a href=\"http://www.huajungroup.com/msr\"><img src=../images/Barner_HJ005.gif border=1 height=62 width=468></a>";
theAds[3] = "<a href=\"http://www.legend.com.cn/\"><img src=../images/Barner_HJ004.gif border=1 height=62 width=468></a>";

var rand = Math.round(Math.random()*10); 

while (rand >3) 
{    rand = Math.round(Math.random()*10); } 

document.write(theAds[rand]);