page Redirect problem

Question

I m using dataset in my page and

                DataSet ds = new DataSet("DataSet");  //dataset belong to another dataset
                ds.Tables.Add(dtxml);
                ds.Tables.Add(dtarllogo);
..........................
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when i go to the next page and click the back button then error(dataset belong to another dataset)
So where can i declare dataset to resolve this problem that when i came back then this error not occur.