why some fields hidden from node? well I have a content type in which I needed about 6 taxonomy fields..

it was working at first but suddenly it stopped showing taxonomy fields in node display page.

I used Field Permissions and Field Group modules and I show the fields in content type's display management. but nothing changed!

although I can use views to get and show the data but it may be an error in my drupal core or something.

Update: I disabled field group and field permissions.. every thing works fine now! but cause I need these modules I should continue trying!
I it been a long time that you created that content type ?

It is on a production website already ?

Are you working on a fresh Drupal 7 installation ?

You could delete and recreate that content type if there is no serious impact on your site or your data.

If you do that, then your can check if the situation happens again. Sometimes there are particular manipulations while working that are responsible for those situations (and you can find out if you did something in a certain way the first time).

But remember : to me this operation depends on the 3 questions that I've asked on top of this text.

Does it help a bit ?