function checkValidReferer ( referring_id ) {
	ajax_request (
		page + ".php",
		
		{
			func:			'checkValidReferrer',
			referring_id:	referring_id
		},
		
		function ( transport, json ) {
			if ( json !== true ){
				$( 'referring_id' ).value = 0;
			}
		}
	);
}