by fcp (Developer) on July 22, 2009 · permalink

Thank you for the suggestion. Actually, some people have already suggested the same feature of disabling visited link styling for cross-domain links on https://bugzilla.mozilla.org/show_bug.cgi?id=147777 (see e.g. comments #83, #89, #113 and #120 there). However, I am a little skeptical about its usefulness for three reasons.

First, one of the most significant advantages of visited link styling is that it allows a user to locate previously visited pages in results of the search engine easily. Disabling visited link styling for cross-domain links breaks this use case completely, and enabling it only for same-domain links is somewhat missing the point.

Second, in my opinion, visited link styling is useful because it is consistent. If visited link styling is enabled for some links and disabled for the others, a user may perceive it as if visited links are only sometimes rendered in a different style at random, making it barely more useful than disabling visited link styling altogether.

Finally, the suggested feature is based on the so-called “same-origin policy,” which I do not like very much. The same-origin policy is an assumption that if a user trusts a page to some degree, he/she will trust the other pages in the same domain to the same degree. Although this assumption is often correct, there are many exceptions such as shared servers and user-provided contents. Every time a browser makes use of this assumption, both the browser developers and the web developers must be very careful not to break security by some combination of unexpected configurations. I do not think that it is the right design of browsers or extensions.

I might implement it in future as an experiment, but do not expect it to happen soon. Thank you for your suggestion.