Hi all, I have a web site in Asp.net which is run locally ok & when uploaded by client it runs ok on mozilla but it gives following error in some cases on IE7. ( eg when click register, cancel button on registration page. Error : Invalid postback or callback argument. Event validation is enabled using <pages enableEventValidation="true"/> in configuration or <%@ Page EnableEventValidation="true" %> in a page. For security purposes, this feature verifies that arguments to postback or callback events originate from the server control that originally rendered them. If the data is valid and expected, use the ClientScriptManager.RegisterForEventValidation method in order to register the postback or callback data for validation. I am not include anything in following enableEventValidation="False" or enableEventValidation="True" How to solve this problem ....... Please give me reply, it's urgent.... Regards, Girish