More hints below

Gmail displays more hints and tricks at the bottom of the window:

Esc-a as a short cut to reply all.

If you're replying to a mail and want to change to reply all from your keyboard, hit Esc then 'a'. This is a keyboard shortcut. Saves a mouse click.

Because Esc moves the focus out of the text box when you are composing a reply, it allows you to then type the normal keyboard shortcuts 'r' for reply-to-sender, 'a' for reply-to-all, or 'f' forward to change the recipients of your message. So if you're replying to a message, the combination Esc then 'a' will change it to "reply to all".

Sign out by clicking on Sign out.

On Netscape/Mozilla/Firefox, if you close the Gmail *tab*, not the window, you're still siged in. Anybody can open a new tab and go to Gmail and automatically get logged into your account. It's just good habit to sign out from Gmail session by clicking on "Sign out" link on the top right corner.

More ways to open composer in a new window

shift + 'c' or shift + click on 'Compose Mail'
shift + 'r' or shift + 'reply'
shift + 'a' or shift + 'reply all'
shift + 'f' or shift + 'forward'
Shift key is needed for keyboard shortcuts to work (caps lock is ignored).

Does Gmail ever ask for my username and password?

"No. We feel strongly about your privacy and security. For your protection, we do not send unsolicited mass messages asking for passwords or personal information. We don't need this information to assist Gmail users.

If you've received a message that asks for private information, like your password, or directs you to a site that resembles Gmail, please note that the message did not originate with Gmail.

This practice is commonly called "spoofing." Spammers spoof by sending a fake email and then setting up a website, in an attempt to collect sensitive personal information and/or gain access to your Gmail account."

Search for "spoof" in the help page for more details.

Many ways to return to inbox

To return to the inbox, you can of course click on the "Inbox" link on the left had side, or if you're in conversation view, clicking on the "Back to Inbox" link above the conversation. There is also green 'Inbox' label text next to the subject. But you can also click on the Gmail logo, a much larger target, to go back to the inbox.

Keyboard shortcut users can type "g i" to Go to the Inbox.

Clicking on the logo, the Inbox link, the Refresh link, or the keyboard shortcut "u" all will refresh the inbox with the latest messages received.

Open composer in a new window

In a conversation there is an icon & link on the right hand side to open it in a new window. The same feature is available when you're composing a message. Need to look up some old message? Click on the icon on the upper right corner of the composer to bring it up in a new window.