function getLink(No){
 var i=0;
 var Stra="a.gif",Strb="b.gif";
 var linkpieces = document.getElementsByName("linkpiece");
 var linkbuttons= document.getElementsByName("linkbutton");
 for(i=0;i<linkpieces.length;i++){
	linkpieces[i].style.display="none";
	linkbuttons[i].src=linkbuttons[i].src.substr(0,linkbuttons[i].src.length-5)+Stra;
	}
 linkpieces[No-1].style.display="block";
 linkbuttons[No-1].src=linkbuttons[No-1].src.substr(0,linkbuttons[No-1].src.length-5)+Strb;
}