Thanks for speedy reply Jason! I used Ray's php method to strip out www. so Cart and Home Page have same address. Worked great, (although I've got that include on the top of Head tag on Home Page and at the bottom of Head tag for cart.php and product_details.php.) Otherwise, I was getting "Headers already sent" error message.
Any reason why that would keep one from advancing to checkout.php form? Checkout button doesn't send one to checkout form, now? (Just reloads page [It looks like?]) All the other buttons work. (Continue Shopping, Clear Cart, Update Cart)
Thanks in advance.