Gmail has come out with latest feature on their Inboxes. Now you are able to view multiple Inboxes only in one page at the same time.  So you no need to open multiple broweser or pages to open multi inboxes. It have reviewed on Official Gmail Blog.

The Octavian “Vivi” Costache, software engineer said ” I’m seriously into filters and labels. All the email I get related to Flash goes under my “flash” label, everything about paragliding goes under “flying,” and they all skip my inbox because that’s how I like to stay organized. But when new email arrives I have to switch to the “flash” label first, then click on “paragliding,” etc. I wanted a way to see it all at once.”

So now your multiple inboxes open problem is solved. Thanks to gmailblog.