function win(target,wi,he){
	//Posicao
	x = (screen.width / 2) - (wi / 2); 
	y = (screen.height / 2) - (he / 2) - 25; 

	features = "toolbar=no, menubar=no, location=no, width="+wi+", height="+he+", scrollbars=yes, resizable=no, left=" + x + ",top=" + y;
	window.open(target, "", features);
}

function checkNull(checkForm){
	var ret = false;

	for(x=0; x < checkForm.elements.length; x++){
		ret = (checkForm.elements(x).id == 1) && (checkForm.elements(x).value == '');

		if (ret){
			alert('O Campo ' + checkForm.elements(x).tagName + ' não pode ser nulo.')
			checkForm.elements(x).focus();
			break;
		}
	}
	
	return ret;
}

function check_contato(){
	return (checkNull(document.form_contato));
}