Quoting Etak <[log in to unmask]>:

> Hello
>    Could someone please explain the difference between
> nominative/accusative languages and ergative/ablative
> ones.  (I think I've got the names right.  I'm not
> even sure about that...)  They seem to crop up at odd
> times in various messages and I don't know what they
> mean.

Others have already explained nom/acc and abs/erg. I just thought I'd mention
that these systems are also known as simply "accusative" and "ergative". Also,
there are other systems possible - the most interesting perhaps
being "active", also known as "fluid-S", in which intransitive subjects are
marked either like the agent-like or like the patient-like argument of a
transitive, the choice being made based, basically, on whether the subject is
perceived as controling the action. Were English active, we'd have "I fall" if
I voluntarily fell, and "me fall" otherwise.

Should you want to know more about active langs, ask Daniel Andreasson for his
paper thereon.

>    Also, what are the "universals" that people
> occasionly mention.  Are they important?

A 'universal' is something that's (supposedly) true for most or all languages.
Some conlangers feel it's important to conform to a reasonably high proportion
of them, to make their langs realistic - others feel that violating them is
good sport. Most universals seem to be broken by one or more natlang; few are
truly "universal" universals.

>    I'm working on an inflecting language and I've made
> the case markers for nouns as suffixes.  Would it look
> too strange, or break some (unknown to me) linguistic
> rule to conjugate verbs by adding prefixes.  Having
> suffixes for both nouns and verbs seems kind of boring
> for my language. :)

Can't think of any natlang that inflects verbs with prefixes, but I'd be most
suprised if there aren't any.

> P.S.  Out of curiousity, is anyone actually fluent in
> their conlangs, like able to speak a conlang without
> having to think too much about it?  How many people
> have conlangs that have developed that far?

Me not.