Ha, you are asking a bunch of programmers which text editor is best?!?
Be prepared for a flood of answers (and the real answer is they're all good once you get used to them).
Sublime Text is the one I've currently fallen in love with. A few months ago it was gEdit. I'm never ever turning back, though - Sublime Text is worlds better.
For basic text editing that will let you concentrate on learning the basic HTML, TextWrangler is free and *much* nicer than Notepad! Strictly speaking, its all you need.
If you want bells and whistles - code completion, debugging, pop-up hints, templates, and are looking at getting into Javascript then have a look at NetBeans. https://netbeans.org/features/html5/index.html - also free.
Otherwise - start trying out the free demos of Coda, Sublime, PHPStorm etc. but they do cost money if you want to keep using them.