function validaEmail(){
	if(!checkMail(document.getElementById('email').value)){
		alert('Informe um email válido!');
		document.getElementById('email').focus();
		return false;
	}
}
function checkMail(mail){
	var er = new RegExp(/^[A-Za-z0-9_\-\.]+@[A-Za-z0-9_\-\.]{2,}\.[A-Za-z0-9]{2,}(\.[A-Za-z0-9])?/);
	if(typeof(mail) == "string"){
		if(er.test(mail)){ return true; }
		}else if(typeof(mail) == "object"){
		if(er.test(mail.value)){ 
			return true; 
		}
	}else{
		return false;
	}
}