Font Size Changes from One Page to Next. HELP!

I've done all I can to avoid posting here, but now I'm lost and we're close to launching the ordering feature.

During the checkout process, the font size suddenly jumps from normal on Step 1 (checkout_shipping.php) to a HUGE unexplainable size on Step 2 (checkout_payment.php).

Although I've made small text changes, I can't find the problem. I even restored the original Zen Cart pages to see if that would solve it. I don't know what I broke or where to go to fix it. Maybe there's a supporting file I need to fix. Any tips or suggestion for what files to check beyond checkout_payment.php?

USING ZEN CART 1.3.8.a

HERE'S MY SITE:
http://www.dmc-on-line.com/Orders/index.php

As we can't proceed to checkout without registering first, it's difficult to say what's affecting this.

Did you at any stage create a custom stylesheet for stage 2 of checkout?

Did you edit the templates (tpl_xxxxxxxxxxx.php) ?

PROBLEM SOLVED...

Thanks for your input. I'm a novice at this stuff, but I was able to narrow down the possibilities and ultimately discovered something I've never seen.

For some reason, two rogue files were on my server with similar names but with weird suffixes; something similar to "checkout_paymentq002.php". I have no idea how these strange filenames occurred or got uploaded, but I'm guessing php freaked out a little. I removed these two strange files and it works fine!

Thanks for taking the time to help.