function formCheck(formobj){
var fieldRequired = Array("nome", "email", "comentarios");
var fieldDescription = Array("Seu Nome", "Seu E-mail", "Seu Comentário");

var alertMsg = "Por favor, preencha:\n\n";

var l_Msg = alertMsg.length;

for (var i = 0; i < fieldRequired.length; i++){
 var obj = formobj.elements[fieldRequired[i]];
 if (obj){
  switch(obj.type){
  case "select-one":
   if (obj.selectedIndex == -1 || obj.options[obj.selectedIndex].text == ""){
    alertMsg += " - " + fieldDescription[i] + "\n";
   }
   break;
  case "select-multiple":
   if (obj.selectedIndex == -1){
    alertMsg += " - " + fieldDescription[i] + "\n";
   }
   break;
  case "text":
  case "textarea":
   if (obj.value == "" || obj.value == null){
    alertMsg += " - " + fieldDescription[i] + "\n";
   }
   break;
  default:
  }
  if (obj.type == undefined){
   var blnchecked = false;
   for (var j = 0; j < obj.length; j++){
    if (obj[j].checked){
     blnchecked = true;
    }
   }
   if (!blnchecked){
    alertMsg += " - " + fieldDescription[i] + "\n";
   }
  }
 }
}

if (alertMsg.length == l_Msg){
 return true;
}else{
 alert(alertMsg);
 return false;
}
}