even if you have 2 ISPs the ASA must have one and only one default gateway. So even if you "static" your web servers to ISP1 IPs and other services to ISP2 addresses there is no way to tell the ASA to route the traffic from web servers to Internet via ISP1 and all the other via ISP2 since you can not perform policy based routing (route maps) on the ASA.
A solution could be partition the ASA in two contexts so that you can have separate routing tables (but you can no longer close VPNs or perform dynamic routing).
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...