Hi, I want to delete parent record and related child record.I have used formula, same works fine for parent record deletion but am unable delete related child record.

Before I answer, I am curious to know what you put in the page close.html.

You should be using a pure script solution and calling QuickBase's API methods using AJAX without loading new pages and subsequently closing them. The response of most of the API methods in QuickBase's API are not intended to be displayed unless they return HTML (most API methods return XML).