So, with multiple sign-in, you can log in to more than one account using the same browser session. You can sign in to ten accounts at a time.
Switching On Multiple Sign-in
Multiple sign-in is supported across a range of Google products like Gmail, Calendar, Google Docs, Google Sites, Reader, Voice, and Google Code. But first you have to enable it.- Go to the multiple sign-in settings page
- Sign in to your account with your default Google username and password.
- Select On to enable the multiple sign-in feature and select the checkboxes to confirm that you understand how to use multiple sign-in.
- Click Save changes.
- Remember – You need to enable multiple sign-in feature in each of your accounts which you may want to open at the same time.
You can read more about it and address any issues you are having via the Official Google page explaining multiple sign-in. The other bit of good news is that multiple sign-in support has been extended to Gmail for mobile too.