After waiting for a long time, Google finally made this feature enabled. Now you can open multiple Gmail accounts in one browser. Till now users can open only one Gmail account in one browser, to open the second account, users had to logout from the previous account. But now it is an old way to login to gmail account. Google has done a great job. Many users wanted this feature that they could log in to multiple accounts in one browser.

To add multiple account in a single browser:

Go to upper right corner of your gmail account -> Click on "Add account" button from dropdown menu -> login with your other gmail account.

That's it.