function valida(){

if (document.form.category2.value==""){
 alert('Inform your name!');
 document.form.category2.focus();
 return false;
}

if (document.form.category3.value==""){
 alert('Inform your e-mail!');
 document.form.category3.focus();
 return false;
}
 parte1 = document.form.category3.value.indexOf("@");
 parte3 = document.form.category3.value.length;
if (!(parte1 >= 3 && parte2 >= 6 && parte3 >= 9)) {
alert ("you must use a valid email address! Ex.: seunome@dominio.com");
document.form.category3.focus();
return false;
}


}