let say we have an ajax that post some data to the server-side, for example some data to be inserted in a table in the database, I think there are two kind of exceptions that could occur :

1) problem inserting data in the database.
2)ajax communication with server side problem.

so each one of the two exceptions above will send a json message back to the ajax so the user will know that :
1) submit was successful.
2)submit was not successful (problem inserting in the database)
3) submit was not successful because of ajax communication problem.

For me this is the theory, can you please give me an example on how to implement the ajax to deal with the 3 above json messages ?

Thanks, your help is appreciated.