var rn=Math.floor(Math.random()*12);  
try{
    if(rn==0) {document.getElementById("1").style.display = 'block'} else {document.getElementById("1").style.display = 'none'}; 
    if(rn==1) {document.getElementById("2").style.display = 'block'} else {document.getElementById("2").style.display = 'none'}; 
    if(rn==2) {document.getElementById("3").style.display = 'block'} else {document.getElementById("3").style.display = 'none'}; 
    if(rn==3) {document.getElementById("4").style.display = 'block'} else {document.getElementById("4").style.display = 'none'};
    if(rn==4) {document.getElementById("5").style.display = 'block'} else {document.getElementById("5").style.display = 'none'};
    if(rn==5) {document.getElementById("6").style.display = 'block'} else {document.getElementById("6").style.display = 'none'};
    if(rn==6) {document.getElementById("7").style.display = 'block'} else {document.getElementById("7").style.display = 'none'}; 
    if(rn==7) {document.getElementById("8").style.display = 'block'} else {document.getElementById("8").style.display = 'none'}; 
    if(rn==8) {document.getElementById("9").style.display = 'block'} else {document.getElementById("9").style.display = 'none'}; 
    if(rn==9) {document.getElementById("10").style.display = 'block'} else {document.getElementById("10").style.display = 'none'};
    if(rn==10) {document.getElementById("11").style.display = 'block'} else {document.getElementById("11").style.display = 'none'};
    if(rn==11) {document.getElementById("12").style.display = 'block'} else {document.getElementById("12").style.display = 'none'};
}catch(e)
{
    document.getElementById("1").style.display = 'block';
}