simg=new Array(8);
simg[0]="img/mainimage.jpg";
simg[1]="img/mainimage1.jpg";
simg[2]="img/mainimage2.jpg";
simg[3]="img/mainimage3.jpg";
simg[4]="img/mainimage4.jpg";
simg[5]="img/mainimage5.jpg";
simg[6]="img/mainimage.jpg";
simg[7]="img/mainimage.jpg";
Myimg=Math.floor(8*Math.random());
document.write("<img src='"+simg[Myimg]+"'>");