function atRandomImg(){ 
   atImg=new Array(); 
   atImg[0] =' <img src="images/chara01.jpg" width="495" height="611">'; 
   atImg[1] =' <img src="images/chara02.jpg" width="495" height="611">'; 
   atImg[2] =' <img src="images/chara03.jpg" width="495" height="611">'; 
   atImg[3] =' <img src="images/chara04.jpg" width="495" height="611">'; 

   var imgNum=atImg.length; 
   var r=Math.floor(Math.random()*imgNum); 
   document.write(atImg[r]); 
}