myD = new Date();
myMonth = myD.getMonth() + 1;


ranimg = new Array();
ranimg[0]="images/photo_main01.jpg";
ranimg[1]="images/photo_main02.jpg";
ranimg[2]="images/photo_main03.jpg";
xx="images/photo_main04.jpg";


if(myMonth>=3 && myMonth<6){
xx = "images/photo_main01.jpg";
}else if(myMonth>=6 && myMonth<9){
xx = "images/photo_main02.jpg";
}else if(myMonth>=9 && myMonth<12){
xx = "images/photo_main03.jpg";
}else if(myMonth<12 && myMonth>=3){
xx = "images/photo_main04.jpg";
}


document.write ('<style type="text/css"><!-- #photo_main {width:802px; height:335px; background:url("'+ xx +'") left top no-repeat; text-align:right;} --></style>');