How to prevent alert message box when browser back button is pressed

Hi sir,

I am running one application where one gridview is there when i am deleting any data there it shows one message for deleting.

for message i used this code:

ClientScript.RegisterStartupScript(this.GetType(), "ShowMessage", string.Format("<script type='text/javascript'>alert('{0}')</script>", "this row is deleted"));

after that i am going to some other page ,after going other page when i click on back button in browser it is coming in the previous page but the message which poped up before again getting popup.

how to restrict this thing?

Thanks.