Nano-10 uses a very primitive file system. File name can only start with one character (0,1,2,....9,A,B,C....)and can have 3 digit extension.
Each file name is alloted with 2K bytes of space but each file name can occupy multiple slot, in which case it takes over the space of other file name.
Hence if your 0.htm definitely occupies < 10K bytes, it can take over the space of 0, 1,2,3,4.xxx and you can put your css file as 5.css, 6.css etc. Your htm file can then refer to these css files.
