> httrack  --mirror --continue
> +http://programmedlessons.org/*
> <http://programmedlessons.org/>

The filter is redundant

> but there were some 404 errors

> turns out it  has files missing
> those files are available at this original mirror
>   <http://chortle.ccsu.edu/>
> 
> how do I tell httrack to look for 404's on this
> other mirror

No way to do that. Are they 404 or are they just not in your mirror? By
default httrack will not go off the starting site.
If the missing files are non-html add the -n (--near) to get all non-html
files

> other mirror, i really don't want to hit them up
> again, its kind of big (250+mb)
--update not continue.