rnd.today=new Date(); 
rnd.seed=rnd.today.getTime(); 
    function rnd() { 
　　　　rnd.seed = (rnd.seed*9301+49297) % 233280; 
　　　　return rnd.seed/(233280.0);
    }; 
    function rand(number) { 
　　　　return Math.ceil(rnd()*number); 
    }; 
var n=rand(12);
if(n==0){
document.getElementById("right").style.backgroundImage="url(img/bgpic.jpg)";
}else if (n==1){
document.getElementById("right").style.backgroundImage="url(img/bgpic1.jpg)";
}else if (n==2){
document.getElementById("right").style.backgroundImage="url(img/bgpic2.jpg)";
}else if (n==3){
document.getElementById("right").style.backgroundImage="url(img/bgpic3.jpg)";
}else if (n==4){
document.getElementById("right").style.backgroundImage="url(img/bgpic4.jpg)";
}else if (n==5){
document.getElementById("right").style.backgroundImage="url(img/bgpic5.jpg)";
}else if (n==6){
document.getElementById("right").style.backgroundImage="url(img/bgpic6.jpg)";
}else if (n==7){
document.getElementById("right").style.backgroundImage="url(img/bgpic7.jpg)";
}else if (n==8){
document.getElementById("right").style.backgroundImage="url(img/bgpic8.jpg)";
}else if (n==9){
document.getElementById("right").style.backgroundImage="url(img/bgpic9.jpg)";
}else if (n==10){
document.getElementById("right").style.backgroundImage="url(img/bgpic10.jpg)";
}else if (n==11){
document.getElementById("right").style.backgroundImage="url(img/bgpic11.jpg)";
}else if (n==12){
document.getElementById("right").style.backgroundImage="url(img/bgpic12.jpg)";
};