function hidediv(divObj,divName) { 

	if (document.getElementById) { // DOM3 = IE5, NS6 
		document.getElementById(divName).style.visibility = 'hidden'; 
	} else { 
		if (document.layers) { // Netscape 4 
			document.divObj.visibility = 'hidden'; 
		} else { // IE 4 
			document.all.divObj.style.visibility = 'hidden'; 
		} 
	} 
} 

function showdiv(divObj,divName) { 
	if (document.getElementById) { // DOM3 = IE5, NS6 
		document.getElementById(divName).style.visibility = 'visible'; 
	} else { 
		if (document.layers) { // Netscape 4 
			document.divObj.visibility = 'visible'; 
		} else { // IE 4 
			document.all.divObj.style.visibility = 'visible'; 
		} 
	} 
} 

function checkForm(formObj) {

	if (formObj.superficie.value == '') {
		alert('valorizzare il campo Superficie.');
		formObj.superficie.focus();
		return false;
	} else if (formObj.categoria.selectedIndex == 0) {
		alert('valorizzare il campo Categorie Merceologiche/Tipologia Utenza Domestica.');
		formObj.categoria.focus();
		return false;
	}
	
	return true;

}