G-Mail keyboard Shortcuts....

Shortcut Key	Definition	Action
c	Compose	Allows you to compose a new message. <Shift> + c allows you to compose a message in a new window.
/	Search	Puts your cursor in the search box.
k	Move to newer conversation	Opens or moves your cursor to a more recent conversation. You can hit <Enter> to expand a conversation.
j	Move to older conversation	Opens or moves your cursor to the next oldest conversation. You can hit <Enter> to expand a conversation.
n	Next message	Moves your cursor to the next message. You can hit <Enter> to expand or collapse a message. (Only applicable in 'Conversation View.')
p	Previous message	Moves your cursor to the previous message. You can hit <Enter> to expand or collapse a message. (Only applicable in 'Conversation View.')
o or <Enter>	Open	Opens your conversation. Also expands or collapses a message if you are in 'Conversation View.'
u	Return to conversation list	Refreshes your page and returns you to the inbox, or list of conversations
e	Archive	Archive your conversation from any view.
m	Mute	Archives the conversation, and all future messages skip the Inbox unless sent or cc'd directly to you.
x	Select conversation	Automatically checks and selects a conversation so that you can archive, apply a label, or choose an action from the drop-down menu to apply to that conversation.
s	Star a message or conversation	Adds or removes a star to a message or conversation. Stars allow you to give a message or conversation a special status.
+	Mark as important	Helps Gmail learn what's important to you by marking misclassified messages. (Specific to Priority Inbox)
-	Mark as unimportant	Helps Gmail learn what's not important to you by marking misclassified messages. (Specific to Priority Inbox)
!	Report spam	Marks a message as spam and removes it from your conversation list.
r	Reply	Replies to the message sender. <Shift> + r allows you to reply to a message in a new window. (Only applicable in 'Conversation View.')
a	Reply all	Replies to all message recipients. <Shift> +a allows you to reply to all message recipients in a new window. (Only applicable in 'Conversation View.')
f	Forward	Forwards a message. <Shift> + f allows you to forward a message in a new window. (Only applicable in 'Conversation View.')