osCommerce troubleshoot- something basic is wrong.

[wenonae]

Hello All-

I'm new around these parts- but ya'll seem really savvy.
I'm just coming up to speed on basic PHP coding.  I am thinking that there's a way to step through a program so that you can pin-point your error. 

My situation for my 'live' shop is that I did some mods to change the invoices and packing slips.  Basically, I make one too many adjustments, now even though I tried to 'un-do' the files I added, my catalog shows up funky.  Has anyone seen something to look like this?
http://www.gnosishealthproducts.com/osCommerce/catalog    It's just ???????????????........ with no info. 

Even if no one has seen the like, maybe suggestions for a 'decoder' program.  I have just run out of creative things to try.

Thanks!
Wen'