Quote (RedBlacks @ Dec 19 2014 06:59am)
Notepad++ or any text editor or ide really.
I personally use atom/sublimetext. Much better than npp.
I'd also definitely recommend getting a CSS preprocessor. LESS or SASS. SASS is more powerful and more useful personally as it has nice commandline watch tasks.
I use Sublime Text as well. Along with Codekit for all the SASS i write.