A client component runs on a user computer in conjunction with a web browser and detects errors, such as but not limited to "404: page not found" errors, in which a requested web page or other object cannot be displayed. In response to detecting the error, the client component notifies an error processing server, which uses the URL of the failed request to identify an alternate object to display. The alternate object may, for example, be (a) an object retrieved from replacement URL, or from a URL that is otherwise related to the requested object, (b) a cached version of the requested object, (c) an object retrieved from a closely matching URL found in the user's clickstream history, or (d) a dynamically generated page that includes links to one or more of the foregoing types of alternate objects. Also disclosed are methods for identifying alternate objects for a given URL.