G-Mail has added one more feature to its repertoire.
Message Sneak Peek, a utility that you can turn on to get message previews without having to leave your inbox and actually open a message. You'll have to enable Message Sneak Peek in your Gmail settings, but once you have it turned on, all you have to do is right-click on message to see a pop-up message preview, complete with the text of your messages.
It is launched in Google Labs and is not the fully developed facility but still you can make use of it.
However from my personal experience i found out that it works well on firefox and chrome but gives problems in explorer(Do comment if it works fine for you).
The message preview appears over your inbox and in the same window: it's not a pop-up window, and it doesn't take you away from your inbox. The preview shows the first several lines of the message, along with archive and delete buttons that allow you to quickly remove the message from your inbox. If the message is image-heavy, you'll see the top of the message and the images will load.
Message Sneak Peek even has a keyboard command bound to it (the "h" key if you have keyboard shortcuts turned on) and once you toggle it, using other key commands to browse to older or newer messages will also update the preview window. Once you use Message Sneak Peek, your message doesn't turn read, and your inbox will still look like you have a new message in it.
To enable it just log in to G-Mail.
Then go to settings (on top right corner).
Then go to labs in settings page.
Search for "Message sneak peak" and enable it and save changes by clicking on button given on top.
Enjoy fast mail viewing.
This feature is only available in new G-mail version
You can upgrade to newer version by clicking 'newer version' present at page footer(at last)
However older versions of explorer might not support it.