After the Launch of new Gmail widget for iGoogle and Gmail for Android 2.3.5, Gmail has launched a new lab feature called “Preview Pane” which permits you to browse emails while you reply to one of your discussion, this new feature is just like the facsimile for Outlook mail.

Preview Pane, which is now accessible in Gmail Labs, enables users to concurrently preview parts of an email while interpretation or responding to others. Users of Gmail for iPad or Android will immediately identify the interface; its design is frankly motivated by the email service’s mobile web apps.

The preview pane facility is not enabled by default but here is the process to turn it on.

1. Log in to your Gmail account.
2. On the top right side of the Gmail page, click on the gear icon.
3. In the dropdown menu that opens, click on “Labs”
4. Scroll down the list of options until you come to “Preview pane”. (It was a long way down on my system.)
5. Click “Enable.”
6. At the bottom of the page, click the button “Save changes.”

After enabling Preview Pane on your gmail, you will observe a toggle button at the top right corner of your mail list, which permits you to switch between preview and list views. In the preview form, you will be provided with an option  to set up a horizontal or vertical split-screen view.