File not found error in Asp.net

My Web Application has to support two browesrs .

IE Mozilla

 sometimes back i created a page in my Appliaction called SessionExpiry.aspx now i have removed that page in my application.

 Now on session expiry Firefox still takes me to the same page and i get the error 404 error i.e.File Not found error where as it works fine in IE 6.0

Any idea how to solve this issue any help would be highly appericated.... Regards Amit Goel
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