This one's handy for those time-specific marketing pages. So for instance, if you add this tag to a page:
< META NAME="GOOGLEBOT" CONTENT="unavailable_after: 31-Dec-2013 23:59:59 EST" >
Then the page in question will vanish from the Google cache on the 1st Jan 2014 EST. You'll no longer appear in the results. Could be fairly neat for some time-critical promotions that you'd like to have appear in search results but want to save yourself the hassle of switching the current page to a version with NOINDEX tags shortly after the thing ends.
This also helps get the job done, since you never can be quite sure when the crawler will come back to your page and see the NOINDEX tags, so this is nice since you can just set it and forget and make no changes to the page when the promotion ends. Nifty.Posted by tomachi on October 6th, 2009 filed in SEO