security exception while displaying a grid with serialization

I'm new in asp.net development my site works well locally and online too except for a page on a subfolder, when I uploaded it to the online hosting server it throughs this exception
Description: The application attempted to perform an operation not allowed by the security policy.  To grant this application the required permission please contact your system administrator or change the application's trust level in the configuration file. Exception Details: System.Security.SecurityException: Request for the permission of type 'System.Security.Permissions.SecurityPermission, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed. S ...