I can't find even the general information about Xomap. No documentation, no manual page, no info page. Google cannot answer too.
I use Nokia n800 and want to install fvwm on it. I know that it is possible to remove Xomap and install other X-server, but there should be a reasons, why new X-server was developed. I mean, maybe Xomap more optimized for n800 and it is better choice to try to install fvwm on it?
So, if somebody knows where documentation on Xomap is, I'll be very grateful for the answer.

Why would you need another X server for fvwm?
Xomap is X for OMAP chipsets (the N800 has a OMAP2 chipset). OMAPs are system-on-chip chips from Texas Instruments.
IIRC Xomap has its origin in the kdrive project for small X servers for embedded systems.
There's IMHO no point in replacing the X server for just changing the window manager. Have you looked at easy-debian for the tablet? There you'll have fvwm.

Great thanks, pycage.
In fact, all easier than it seemed.
My fault. Don't know, why has not seen an abbreviation "OMAP" in "Xomap" :]