If you use multiple Google accounts – say one for gmail another for adsense and yet another for Reader, you would know that you can sign into only one account at a time in a browser. Of course you could use separate browsers for each of the account, but it is hassle to do so.
Here is a great alternative. Google has an advanced feature that lets you sign into multiple Google Accounts simultaneously in the same browser.
To do so go to https://www.google.com/accounts/b/0/MultipleSessions.
Enable the multiple sign in feature for your primary account. Once signed in, you can click the arrow next to your address (at top right) to switch between accounts. The account that you’re currently using is displayed at the top of most Google product pages. Make sure that you are using the account that you want.
However, multiple sign-in does not work with all Google products. Presently it works with Gmail, Reader, Calendar, Google Code, Google Sites and Google Voice. The other Google products will default to the first account into which you signed using your current browser session.