Magento Admin: 404 Error Page not found.

mag-admin-404Let’s suppose you are logged in to Magento admin panel and you are installing a new extension that adds some new sections to Magento Configurations.
You activate your new extension and it adds some new tabs/sections but when you click on newly added tab you see a 404 error, don’t worry!

Solution :

Just logout from admin panel and login again. Cheers!!!