Seems that checking for “malware delivering websites” using Norton’s Anti-phishing function is redundant when using Firefox. If this is so with the browser you’re using, I’d turn off the Norton function.
In Oliver Fisher's blog post "Cross-site Warnings" he mentions the use of Google "Blacklists" by several browsers for the purpose of identifying websites that are compromised or contain compromised content from other servers.
Extract from Blog post:
"Several browsers use data from Google's malware list to protect users. Firefox 3, Chrome and Safari all check sites that users are visiting against Google's list and warn users if they are about to visit a dangerous site. There are some small differences in implementation across browsers that can cause confusion.
All three browsers check the address of the top-level page a user is navigating to. That protects most users in most cases. But, a web page can include content from another web page and if the included content is malicious then users may be exposed. Chrome (and Safari*) [and Firefox 3.5+] check every request against Google's malware list. This means those browsers will protect users even if malicious content from a flagged page is embedded on a non-flagged page.
Updated: FF3.5 checks every request against the blacklist and helps better protect users. FF3.5, Chrome and Safari all behave the same now."
