function rnd_image(){

   var now = new Date();


   var sec_divide = now.getSeconds();

   rnd_number = Math.floor(sec_divide/5); // /20=0, 1, 2  /10=0, 1, 2, 3, 4, 5  etc...

   document.write('<img src="images/home' + rnd_number +'.jpg">');

}

// -->