function switch_img(node,img){
	 var n=navigator.appName;
         var v=parseInt(navigator.appVersion);
         var browsok=((n=="Netscape")&&(v>=3));
         var browsok2=((n=="Microsoft Internet Explorer")&&(v>=4));
         var browsok3=((n=="Opera"));
         if ((browsok)||(browsok2)||(browsok3)) {
	 	 document.images[node].src=img;
	 }
}