Non-Patent Prior Art: Web Pages

Recently I posted (here) about the use of software screen shots of as prior art, under the "known or used by others" prong of 102(a). Web pages are another kind of prior art which I see a lot. Pages from a website are considered publications and thus also available under 102(b). What sort of evidence of a publication date is an Examiner required to provide for a web page?

In most of the cases I've seen involving a web page as prior art, the Examiner used an Internet archive website (such as www.archive.org) to obtain evidence of the publication date. An archive site works as follows: type in a website URL, and the archive provides a list of dates for which past pages from that site are available; choose a date, and the archive serves up the website as it existed on that particular date; thus, you can browse to a copy of a particular page as it appeared on the website in the past.

The MPEP does not mention Internet archives, but does state that the critical date is "the date the item was publicly posted:"

Prior art disclosures on the Internet or on an on-line database are considered to be publicly available as of the date the item was publicly posted. Absent evidence of the date that the disclosure was publicly posted, if the publication itself does not include a publication date (or retrieval date), it cannot be relied upon as prior art under 35 U.S.C. 102(a) or (b). 
(MPEP 2128.)

The BPAI appears to approve of the use of archived web pages as evidence of an electronic publication date. I found two decisions in which the Board found an archive date to be sufficient evidence, and I found no decisions to the contrary.

In Ex parte Shaouy, the Examiner indicated that the web page was available in "internet archive 'wayback machine' " and provided a copy of the web page as retrieved from the archive. The copy contained the following URL at the top of the page: "http://web.archive.org/web/20001209085500/http://www.forecastpro.com/". The Board noted that the numbers encoded in this URL correspond to the date the Examiner used as a publication date (December 9, 2000). The Board found that the Examiner's reference to "internet archive 'wayback machine' " in the Advisory Action, in combination with the date stamp encoded in the URL, was sufficient evidence of a publication date. 

Ex parte Molander contained a similar fact pattern. The Examiner referred to the archive site and the archive date in the rejection. The print out of the archived web page included the URL of the archive site, and that URL encoded the date relied on by the Examiner. The Board once again found that this was sufficient evidence of a publication date for the web page.

So if the rejection isn't very clear about the date relied on for a web page reference, it's probably a good idea to look at the print out of the archived web page, and to check the encoded archive date for yourself.