My first softwares I’ve used for edit HTML and CSS files is Notepad.
And then, when I was looking for some more convenient editors, I found PSPad and TopStyle Lite.
PSPad is used for editing (x)HTML file.
TopStyle Lite is for CSS files. (There is also TopStyle Pro with some advanced feature, but I like the simple of TopStyle Lite).
They are both free and good enough to edit.
===Note for Unicode Editing in PSPad: ===
Unicode (utf-8) is not default setting for new file in PSPad.
To edit utf-8, click Menu: Format > UTF-8.
To change option(s) for saved UTF-8 files, click Menu: Settings > Program Settings > Program Behavior
