I have properly binded the sqldatasource1 to GridView1 and Connectionstring is also correct.I have placed these 2 things(GrudView1 and sqldatasource1 )in same <td> of the table.
Checking everything!But why problem?

Error:
The DataSourceID of 'GridView1' must be the ID of a control of type IDataSource. A control with ID 'SqlDataSource1' could not be found.
Vedavathi