Hi ajay,
If you want to reflect the changes of master page to all site with activating publishing feature, you need to use the SharePoint Designer to check in your customized master page and select the option "Publish a major version", then approve
the master page from your SharePoint site master page gallery.
If you want to reflect to the sub-sites without activating publishing feature, you can "Reset all subsites to inferit this Site Master Page setting" (and sytem master page) from the TopSite->Site Actions->Master page->Site Master Page settings.
Thanks
Regards, Daniel