Null comparison

I am migrating to postgress from msql and am encountering numerous problems
in the differences in NULL usage and comparison.

1. Why are 2 fields not equal if they are both NULL?

2. Is there a way to easily modify my sql select statements to account for
either column being NULL and having them return true if they both are NULL?select a.name, b.cost from a, b where
a.type=b.type

I'd like to make this as easy as possible so I can put it into a
"translation" function.  Currently I have a regsub that handles <> and
NULLs, since <> doesn't work on a NULL field.

thanks,
Al

pls cc me on your response.