Those who have an iPad here, must be aware of 3 pane view of Gmail which actually makes reading email easier. Now, those who wants to enable this feature on web interface of Gmail, they can enable it by a new option in Gmail labs called “Preview Pane”. This feature will transform your Email view into 3 pane and along with it, you will get a toggle switch to interchange between 3 pane and normal interface.
This is my Gmail interface looks like after enabling Preview Pane feature:
As of now, I have enabled Pane view on my web interface of gMail and I also suggest you to try this new feature. You can enable preview pane option from Gmail lab setting page.
Do let me know if you liked this new view of Gmail or you prefer the classic view. Also I would suggest you to check out: 5 Gmail lab feature to increase productivity.