1) how can I find a Mosaic for Sparc-NetBSD

you can probably use lesstif (http://www.hungry.com/) for this.  i haven't
tried it personally, but, i plan to sometime soon.
   
   2) how can I cancel this messages:
   startsun netbsd: zs0a: fifo overrun
   
   when I use my serial port at 38400 baud ???

how often do you get these ?  what sort of sparc do you have ?

i get these very infrequently on my sparc ELC, running pppd at
38400 connected to a 28k8 modem.  i just ignore them.

.mrg.