> Hi,
> Every thing was working fine ..a little earlier  but  not now ...on
> any updation or deletion .... it shows the folowing messages y is that
> so
>
> Slony-I: Table name is replicated and cannot be modified on a subscriber
> node
>
> Any help will be highly appreciated

That seems pretty self-explanatory.

The table is being replicated using Slony-I, and it therefore cannot be
modified on a subscriber node.

Slony-I is preventing you from corrupting the replicated state of that table.

If it didn't do so, you could change data on subscriber nodes so that they
wouldn't be properly replicated anymore.

The bug is that you are trying to modify data on the wrong node. 
Subscriber nodes are _query only_.  Updates for the replicated table must
be performed on the provider node, and nowhere else.