but1 = new Image() ;
  but1.src = "images/top_btn1_off.gif";
  but2 = new Image() ;
  but2.src = "images/top_btn1_on.gif";

  but3 = new Image() ;
  but3.src = "images/top_btn2_off.gif";
  but4 = new Image() ;
  but4.src = "images/top_btn2_on.gif";

  but5 = new Image() ;
  but5.src = "images/top_btn3_off.gif";
  but6 = new Image() ;
  but6.src = "images/top_btn3_on.gif"; 

  but7 = new Image() ;
  but7.src = "images/top_btn4_off.gif";
  but8 = new Image() ;
  but8.src = "images/top_btn4_on.gif";
  
  but9 = new Image() ;
  but9.src = "images/top_btn5_off.gif";
  but10 = new Image() ;
  but10.src = "images/top_btn5_on.gif";

function chkVer(imagename,objectsrc)
{
var n=navigator.appName
var v=parseInt(navigator.appVersion)
var browsok=((n=="Netscape")&&(v>=3))
var browsok2=((n=="Microsoft Internet Explorer")&&(v>=4))
if ((browsok)||(browsok2))
document.images[imagename].src=eval(objectsrc+".src")
}