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.