A price comparison and adjustment system can be used in the context of an Internet environment. The system is generally comprised of a server based browser, a shopping cart manager, an extract and verify module, a validation module, and a counter offer module. The system provides an Internet shopper with a convenient method for comparison shopping online while allowing the shopper control over the comparison-shopping search, which also enables a host merchant to counter offer prices at rival merchant's web sites. The system also provides information about rival merchants to the host merchant, which allows the host merchant to develop an optimal pricing and counter offer strategy. The system creates a portable virtual shopping cart that allows the Internet user to browse rival merchants without the appearance of leaving the host merchant's web site, and further allows the shopper to quickly return to the host merchant's web site to purchase items in the virtual shopping cart.