Works fine in IE, usually is the other way around.
Haven't worked on formatting much yet, still trying to get the workings working. http://www.ihatemyfurnace.com/goodman.html
Use the sample model number "gmp0503".
After submit it writes a cookie and takes you to a page where all of the parts pictures and numbers are dynamically generated. Then you add your parts to your shopping cart and click the checkout button.
Firefox always ends up at PayPal with an empty cart. Pulling my hair out trying to figure out the problem.
The cart script I got from http://simplecartjs.com
Pretty simple to implement but I'm not 100% sure I'm doing it right.