Still no response from RBSWorldpay regarding their reason for filtering of all important base href tag. I tried what Philip suggested in post 333 using java script to split up the tag to fool the filtering but I get a blank page after the transaction has been made. Perhaps it is time for Zencart and RBSWorldpay to part company? I have used Worldpay for the last 9 years, perhaps it is time to try someone else, any suggestions?