Not clear about the addressing description you have here.
First if the web server is on the inside, it has to have an ip address on the same subnet as the inside.
Then if the inside subnet is a public address, you can do a static nat translation that is actually still using the same address of the server, as long as your isp knows that that inside address is yours and route traffic destined for it back to the pix.
Try and look at this link for some further information:
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...