function show_div_change(lay) { 
	if(this.prev_lay){ 
	// document.getElementById(this.prev_lay).style.display="none"; 
		document.getElementById(lay).style.display="block"; 
	} else { 
		document.getElementById(lay).style.display="block"; 
	} 
	this.prev_lay=lay; 
} 

function hide_div_change(lay) { 
	if(this.prev_lay){ 
		document.getElementById(lay).style.display="none"; 
	} else { 
		document.getElementById(lay).style.display="none"; 
	} 
}