Gmail shortcuts.

If you are using the Google's Gmail, you will save time using keyboard shortcuts.
To enable keyboard shortcuts, logon to Gmail and click this link.
Once enabled, you will have these very usefull shortcuts available.

c (compose message)
n (next message),
p (previous Message)
u ( return to conversation list)
r (reply)
g then a (go to all mail)
g then i (go to inbox)

For a complete list view the Google's Gmail help.