Why do I get errors from mountd (can't change attributes for ... bad exports list line ...) ?

[Yuri]

I am getting these errors in messages:
Oct 30 14:37:20 eagle mountd[4243]: can't change attributes for /usr/local
Oct 30 14:37:20 eagle mountd[4243]: bad exports list line /usr/local 
-maproot
Oct 30 14:37:20 eagle mountd[4243]: can't change attributes for /usr/home
Oct 30 14:37:20 eagle mountd[4243]: bad exports list line /usr/home -network

Here is my /etc/exports:
/usr/diskless -alldirs -maproot=root -ro -network=10.0.0 -mask=255.0.0.0
/usr/local -maproot=root -ro -network=10.0.0 -mask=255.0.0.0
/usr/home -maproot=root -network=10.0.0 -mask=255.0.0.0

What's wrong?

Also why messages are so cryptic? Which attributes? Why "bad exports 
list line"?
If it would explain in messages what's wrong I wouldn't even be asking 
question here.

Yuri