If you are still wondering whether to start messing with your site and the authorship tag (rel=author) that Google now supports the advice is that you should not be hesitating. The authorship tag whose attributes are: rel=author is a markup which allows Google to take note of authorship of web content.
Why is this important? For many reasons not least of which that of duplicate content where content which you have written has been copied or scraped. Google now has a sure-fire way of telling which of the identical copies of content is the original one, and treat it accordingly even when, as it so often happens, the site which contains stolen or scraped content, ranks higher than the original one.
Google’s long term plan is to get rid of pagerank as a ranking signal (or discount it entirely) thereby killing off the link-building industry with which it has been fighting a losing battle for years and put in its place a different way of assessing a website’s importance based on authority.
As a matter of fact there are now some very distinct advantages to applying the rel=author tag on your website. Namely:
01. Authorship. By linking your website content, or even the content of a site to which you contribute you identify yourself as the author of that content and irrevocably claim it as your own. This is great news for individual content producers such as writers and journalists and it is also good news for webmasters who produce regular content on their websites.
02. Authority. When it comes to your own website, having a number of pages of high quality, unique content, linked to your name creates a certain degree of authority for your website, for your name, and for the website associated with your name and, even, the subject matter associated with the content which is linked to your name.
03. Brand building. One of the ideas behind the rel=author tag is that it allows a content provider (writer, journalist, freelancer, webmaster) to begin building up their brand by visually identifying themselves with their content not just on their website but across the web (there are options for including this on multi-author websites and one-off posts).
04. Ranking. While ranking is still relevant to a website which is the main presence of an online business, it is also now becoming important to individuals who may want to become associated with a particular product or service. Google has already started to include authorship signals in its ranking but this is still at a relatively young stage as the concept is worked out and more data is gathered.
Google makes a convincing argument of this with Matt Cutts and Othar Hannson explaining first the Authorship Markup in the video below:
and then the Authorship Markup if you are using URL parameters (a little more technical)
What you need to know is how it will benefit you and how to apply it. Well, it helps with search ranking and authority (which may soon become more important than PageRank ever was) and it certainly helps with personal branding.
If you want to apply it Google offers several ways to do it and for any of them the requirement is that you have a Google Plus Profile already in place (if not then this is a great opportunity to create one):
Single Author Blogs and Websites
If you publish a blog or site featuring content by a single author, the simplest way to identify author information is to add a link to your Google Profile on every page, like this:
<a rel="author" href="https://profiles.google.com/109412257237874861202">About Matt Cutts</a>
rel="author" tells Google that Matt is the creator of the site.
Linking multiple author pages
An author page on a site can often link to other web pages about the same author, such as the author's home page or a social networking profile. To tell Google that all these profiles represent the same person, use a rel="me" link to establish a link between profile pages.
Say that Matt is a frequent contributor to http://foo.example.com. Here's a link from his http://example.com author page to the page he maintains on http://mattcutts.com:
<a rel="me" href="http://mattcutts.com">Read more about Matt</a>
In turn, Matt's profile on http://mattcutts.com points back to his author page on http://foo.example.com, like this:
Matt has also written <a rel="me" href="http://foo.example.com/contributors/mattcutts">lots of articles for the Foo Times</a>.
The reciprocal rel="me" links tell Google that the profiles at http://mattcutts.com and http://example.com/contributors/mattcutts represent the same person.
If any of this sounds too technical Google also has a way for authors to establish authorship using nothing more than an email address. Full details of this can be found at the Official Google Help Page.
UPDATE 03.09.2012 It has been some months now since the original post on authorship was written and it has become necessary to revisit it and add a few clarifications. The importance of authorship across the web has risen and it is now becoming imperative to claim your content by linking to it from your Google Profile. This is as important to bloggers and writers as it is to companies and marketers.
Google's Head of Spam Team, Matt Cutts, has pointed out that although backlinks may be under scrutiny and Google's subsequent updates have been designed to look at the quality of links and penalize any attempt at gaming Google's algorithm, backlinks are still a valid ranking factor and should not be abandoned as a valid SEO strategy just yet.
For a step-by-step guide on how to show your Author Photo on Google's search you should check out the Virante Guide, it is about one of the best there is.
The Role of the Writer in the Social Media Age
Here’s What’s Wrong With the Publishing Industry
The Social Media Mind: How to Develop Impeccable Social Media Credentials Fast (podcast)
How to Succeed as a Blogger after the Google Panda Update