How to get Error from application

Sub Application_Error(ByVal sender As Object, ByVal e As EventArgs)
        Dim ErrStr As String
        ErrStr = "Some Error Has Occured in Websit" & vbCrLf
        ErrStr &= "Error Information Are Given Below" & vbCrLf
        ErrStr &= "---------------------------------------" & vbCrLf
        strError &= Server.GetLastError().ToString  +  vbCrLf
        SendMail("naween@gmail.com", "naween@live.com", "UnHandeled Exception Error", ErrStr)
 End Sub