I believe the site could look better for Mozilla users. I don't use Mozilla on a daily basis, I use Avant Browser which is just a shell over IE so everything looks good to me when I view the site normally. It is just when I am in FireBird testing things which
is where I notice the problems.
From this aspect though I do know how it can be difficult to code for multiple browsers because I have done it with many sites but I will say it is worth if you take the time because then "ALL" of your users will be happy.