function valida(form,name) {
	var id = new Array('nome','empresa','email','interesse');
	for (i=0; i <= id.length-1; i++) {
		if (form.elements[id[i]].value == '')
				return action(form,[id[i]],'obrigatório');
		if ([id[i]] == 'email') {  
			valido = /^[a-zA-Z0-9][a-zA-Z0-9\._-]+@([a-zA-Z0-9\._-]+\.)[a-zA-Z-0-9]{2}/;
			if (!valido.exec(form.elements[id[i]].value))
				return action(form,[id[i]],'inválido');
		}
	}
}

function action(form,campo,atrib) {
 	clean();
	var parent  = form.elements[campo].parentNode;
	var content = parent.innerHTML;
	var alerta  = '<span id="alert">Campo '+campo+' '+atrib+'!</span>';
	parent.innerHTML = content + alerta;
	setTimeout (function (){form.elements[campo].focus()}, 0);
	return false;
}

function clean() {
	if (get = document.getElementsByTagName('span')) {
		var i=0;
		while (i <= get.length-1){
			get[i].style.display = 'none';
			i++;
		}
	}
}