Unable to validate data

[Maher Elsayed]

i have this error. [HttpException (0x80004005): Unable to validate data.] System.Web.Configuration.MachineKey.GetDecodedData(Byte[] buf, Byte[] modifier, Int32 start, Int32 length, Int32& dataLength) +195 System.Web.UI.LosFormatter.Deserialize(String input) +60 [HttpException (0x80004005): Authentication of viewstate failed. 1) If this is a cluster, edit configuration so all servers use the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster. 2) Viewstate can only be posted back to the same page. 3) The viewstate for this page might be corrupted.] System.Web.UI.LosFormatter.Deserialize(String input) +116 System.Web.UI.Page.LoadPageStateFromPersistenceMedium() +101 [HttpException (0x80004005): Invalid_Viewstate Client IP: 10.1.1.1 Port: 7332 User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; FunWebProducts; .NET CLR 1.0.3705; FDM; .NET CLR 1.1.4322; .NET CLR 2.0.50727) ViewState: 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 Http-Referer: https://www.egypt.gov.eg/arabic/services/coc/COCService/commonpage/ReqStatus.aspx Path: /arabic/services/coc/COCService/commonpage/ReqStatus.aspx.] System.Web.UI.Page.LoadPageStateFromPersistenceMedium() +446 System.Web.UI.Page.LoadPageViewState() +18 System.Web.UI.Page.ProcessRequestMain() +447