function show_this_block_and_close_all_other ( selected_block_id )
{
	var i = 1;
	
	while ( true )
	{
		var o_block = document.getElementById ( "block_" + i );
		
		if ( o_block )
			o_block.className = "not_visible_element";
		else
			break;	
		
		i++;
	}
	
	var o_selected_block = document.getElementById ( selected_block_id );
	
	o_selected_block.className = "visible_element";
}