Cannot checkout

I have not been able to checkout on my zencart located at https://www.mostwantedstuff.com/store. I beleive its the shipping and the billing conflicting because once you get to step two of the checkout you cannot go any further. I am using authorize.net for my payments so once a customer puts in their billing information and clicks continue to go on to step three it just goes back to step two. I have even tried to enable accepting money orders but it still does the same thing. I have had four seperate programmers try to help me but no luck yet. Everyone has figured out it is the shipping/billing but no success in trouble shooting. Has anyone else had this problem?

AuthorizeNet wants a secure server ...

What happens if you turn off the SEFU?

What happens if you switch to Classic?

NOTE: check your site in FireFox ... the colors are all wrong ...

Thanks so much Linda you are truly a lifesaver. I have been trying to figure this out for over a month now. Turning off the Search Engine Urls worked. I guess I can live without them. Thanks again

Thanks you for the update ... perhaps later on someone can help you figure out a functional SEFU for your site that does not break it ... :smile: