WordPress at a glance
filter is not described

ms_site_check filter-hook . WP 3.0.0

Filters checking the status of the current blog.

Usage

add_filter( 'ms_site_check', 'filter_function_name_2553' );
function filter_function_name_2553( $null ){
	// filter...

	return $null;
}
$null(true/false)
null Whether to skip the blog status check.
Default: null

Where the hook is called

ms_site_check()
wp-includes/ms-load.php 79
$check = apply_filters( 'ms_site_check', null );

Where the hook is used (in WP core)

Does not used.