I know there is some consensus on at least the "no linkjuice awarded" aspect of the nofollow attribute between all of the major search engines. However, there are a few differences, apparently, in other implementation details. I guess I should be impressed that they embraced the same concept at all, and even used the same syntax to denote it.
I've noted the following. I believe Google was the search engine that first advocated the attribute for the purpose of combating link-spam, and they seem to be the only one that truly follows the jist of the phrase "nofollow." To Google, in my experience, and according to Danny Sullivan here, nofollow means that Google will not even follow the link. It's not just that it's not a vote -- it just plain doesn't exist.
That's a somewhat important distinction, as I've seen Yahoo record "nofollow" links to pages on my blog, which is relatively new, here. I'm not quite sure about MSN.
More info here (Yahoo post), and here (MSN post), but neither seems to raise information regarding that particular implementation detail. It's just something I noticed.
July 3rd, 2006 at 10:55 am
[...] Therefore, my hunch is that the link’s value is deprecated to perphaps the level of a typical non-”.edu” link. This is because a home directory site is not under the auspices of the university — at least sometimes. Interestingly, Yahoo! has the said link up high in the list of inbound links, and Yahoo! has the nice feature of collating the links in order of importance. It must be worth something. But I won’t get my hopes up. Yahoo also enumerates some “nofollow” links at the top of the list of backlinks as well. [...]