merge TTF font files (for using in CSS)
Maybe somebody did do this:
I have several files for one font for each style (regular,bold, italic, italc-bold) font-italic.ttf font-bold.ttf font-regular.ttf
How can I merge it to one file, to use in one font-face in CSS?
You cannot. A single font file describes the glyphs used for a particular font in a particular style.
While you could probably merge them and use Stylistic Sets to refer to the different fonts that is something you cannot do in CSS (and most other applications neither). Apart from that (and things like Arabic) there is (as far as I know) no straightforward way to have different glyphs for the same code points in a font file.