Many users have more than one gmail account and would like to login all email accounts at the same time on same browser but by default gmail setting does not allow you to open all accounts at same time. It is an frustrating to check all gmail id one after another.
Gmail Multiple Sign-In feature allow you to login more than one account at same time on the same browser. This method is easy but limited to Google Docs, Gmail, Calender & Reader.
Step 1– Firstly Click here—Login to gmail–Select all options as shown in the below image–Save—Sign out gmail for this setting to take effect.
Step 2– Login gmail again–Click on the email at top of the page–then Click on Sign in to another account–then login your other gmail account.
Now you can login to all gmail account on same browser.
Some other options to open all gmail account
Multiple Browser
Master Gmail Account (Emails Forwarding)
Browser Add-ons etc