electric-indent-mode is enough to keep your code nicely aligned when
all you do is type. However, once you start shifting blocks around,
transposing lines, or slurping and barfing sexps, indentation is bound
to go wrong.
aggressive-indent-mode is a minor mode that keeps your code always
indented. It reindents after every command, making it more reliable
than electric-indent-mode.
This package is available fom Melpa, you may install it by calling
M-x package-install RET aggressive-indent
Then activate it with
(add-hook 'emacs-lisp-mode-hook #'aggressive-indent-mode)
(add-hook ’css-mode-hook #'aggressive-indent-mode)
You can use this hook on any mode you want, aggressive-indent is not
exclusive to emacs-lisp code. In fact, if you want to turn it on for
every programming mode, you can do something like:
(global-aggressive-indent-mode 1)
(add-to-list 'aggressive-indent-excluded-modes 'html-mode)
If you don’t want to install from Melpa, you can download it manually,
place it in your load-path and require it with
(require 'aggressive-indent)