i have some problem  on module i create my on module then i put on page when i click on button the error coming 

A critical error has occurred. An unexpected error has occurred

when i see page Event Viewer it showing this error 

AssemblyVersion:7.2.0

PortalID:0

PortalName:My Website

UserID:1

UserName:host

ActiveTabID:128

ActiveTabName:Speed

RawURL:/en-us/Speed

AbsoluteURL:/Default.aspx

AbsoluteURLReferrer:http://localhost:15253/en-us/Speed

UserAgent:Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.2; Trident/6.0)

DefaultDataProvider:DotNetNuke.Data.SqlDataProvider, DotNetNuke

ExceptionGUID:d74d6117-623b-4fc9-a56f-1d353e7d3e27

InnerException:Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster. http://go.microsoft.com/fwlink/?LinkID=314055

FileName:

FileLineNumber:0

FileColumnNumber:0

Method:

StackTrace:

Message:

DotNetNuke.Services.Exceptions.PageLoadException: Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster.

http://go.microsoft.com/fwlink/?LinkID=314055 ---> System.Web.HttpException: Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster.

http://go.microsoft.com/fwlink/?LinkID=314055 ---> System.Web.UI.ViewStateException: Invalid viewstate. 
	Client IP: ::1
	Port: 12837
	Referer: http://localhost:15253/en-us/Speed
	Path: /Default.aspx
	User-Agent: Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.2; Trident/6.0)
	ViewState: 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...
   --- End of inner exception stack trace ---
   at System.Web.UI.ViewStateException.ThrowError(Exception inner, String persistedState, String errorPageMessage, Boolean macValidati )
   at System.Web.UI.ObjectStateFormatter.Deserialize(String inputString, Purpose purpose)
   at System.Web.UI.ObjectStateFormatter.System.Web.UI.IStateFormatter2.Deserialize(String serializedState, Purpose purpose)
   at System.Web.UI.Util.DeserializeWithAssert(IStateFormatter2 formatter, String serializedState, Purpose purpose)
   at System.Web.UI.HiddenFieldPageStatePersister.Load()
   at System.Web.UI.Page.LoadPageStateFromPersistenceMedium()
   at System.Web.UI.Page.LoadAllState()
   at System.Web.UI.Page.ProcessRequestMain

please help me how to handle this error .............. ASAP thanks