<script language="JavaScript">   
     <!--   
     var a=Math.round(Math.random()*3)   
     image = new Array();   
     image[1]="шапка 1 "     
     image[2]="шапка 2 "   
     image[3]="шапка 3 "   
     document.write ("<img src="+image[a]+"");   
     //-->   
     </script>