Ad-Blocker for Gmail will hide Gmail ads, so that the message takes up the entire width of the screen (even in a new window), and will also hide the useless links that appear at the bottom of the page.
Keep in mind you will need to reload Gmail after you install this addon.
Hide the ads that appear below the message.
Hide the useless links that appear at the bottom of the page, and only show the useful ones.
Hide the "Invite a friend" box on the left.
Decrease the width of the "Compose mail" textarea (plain text only) to behave like it used to in older versions of
Gmail (plain text textarea used to be the same width as the fake textarea displayed at the bottom of an email before you click on it to reply).