function toggleImage ( id_image ) {

	if ( document.getElementById('bigimage1') )  
		document.getElementById('bigimage1').style.display = "none" ;
	if ( document.getElementById('bigimage2') )  
		document.getElementById('bigimage2').style.display = "none" ;	
	if ( document.getElementById('bigimage3') ) 
		document.getElementById('bigimage3').style.display = "none" ;		
	if ( document.getElementById('bigimage4') )  
		document.getElementById('bigimage4').style.display = "none" ;

	document.getElementById(id_image).style.display = "block" ;

}