Thank you for your quick reply, Jason.
In response, I also noticed that the guest form element was posting to the cart page as well. Did you click the "checkout" button on the cart page after you used the guest form element (link)?
If not, this is where you will notice the 404 error when the cart page attempts to redirect to the checkout page. Its as if the checkout page does not recognize the guest session variable and returns the 404 error.
Please note that when I initially inserted the guest session variable to the cart page (even though there appeared to be no access restriction code) and uploaded the file to the server, the 404 error code was still popping up. This is what led me to reply back earlier.
So that you can see what I am talking about, let me insert the guest session variable as you recommended (to the cart page) and I will reply back with a notice to try guest login.
*** Since my cart page has no access restriction code, do you recommend a location where to insert the guest session variable?
