var randomnumber;
var x;
var books;
books = 4;
randomnumber = Math.floor(Math.random() * books);
randomnumber = randomnumber + 1;
switch(randomnumber)
{
case 1:
document.write('');
document.write('
');
break;
case 2:
document.write('');
document.write('
');
break;
case 3:
document.write('');
document.write('
');
break;
case 4:
document.write('');
document.write('
');
break;
}