System.Web.HttpException' occurred in System.Web.dll but was not handled in user code

hi I have code that in this line:

Response.Flush();

this error happen:

An exception of type 'System.Web.HttpException' occurred in System.Web.dll but was not handled in user code Additional information: An error occurred while communicating with the remote host. The error code is 0x800703E3.

what is above error?

Best Regards

Neda