problem with firefox pop up and custom fields

hi,

when I use firefox and I click on the "+" sign to add a product in your shopping cart from the home site that does not work, it does nothing. Why?

if I add a custom field in a product by the administration of virtuemart, then I open the product in the front end and the site crashes. Why?

thank you very much I hope for a response
greetings

all posts have at least one answer ... my no! : (
I need some help, I paid I too like the others, and I have a problem with the site structure that does not depend on me!

please help me, thanks