The page cannot be displayed

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I have several linkbuttons in my main page (default.aspx), and each of them
has a Javascript

funtion that handles the click event and launch a new web page.

Some pages are launched without any parameters (a query string)
(window.open(Ad min.aspx, '', 'menubar=0,

resizable=1, scrollbars=1, left=0, top=0, width=200, height=100');), some
pages do require

parameters (window.open(Ca tPage.aspx?CatN o=' + catNumber + ', '',
'menubar=0, resizable=1,

scrollbars=1, left=0, top=0, width=200, height=100');)

CatNo is the parameter I refered to.

If I keep launching/closing the Admin page (admin.aspx), I keep the main
page "live."

If I just keep refreshing the main page, or launching/closing the Cat page
(CatPage.aspx), the main

page "lives" for about 15 minutes, then I get a "The page cannot be
displayed" error when launching

the Cat page or refreshing the main page.

How can I keep my main page live?

Thanks.