Response.Redirect cannot be called in a Page callback?

Hello,
I am using client callback method on body onload event.I am using image button click event to transfer to 3rd party api.
when I click back button of that api to redirect my site I am getting this error "Response.Redirect cannot be called in a Page callback?"
and now my clients IIS server getting flooded with this error,Please guide me.
 
Regards,
Sushant Tanwade 
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