How do I indicate my Web pages are going to expire?

There is indeed, and I know exactly what you're talking about as I often search for festivals and street fairs just to find information from 2005 and 2006, but nothing about 2007 events. Part of it is because many event sites just aren't organized very well (for example, if you have an annual event, I would suggest that a filename like "craft-fest-2007.html" is less desirable than the simpler -- and more easily replaced each year -- "craft-fest.html")

Better, though, is that there is an HTML "meta" tag that lets you specify an exact expiration date for your Web information, a tag that is respected by Google and most of the other big search engines. It's the "expires" meta tag and according to the spec, here's how you use it:

This is clunky and arguably it's more about when the search engine should get a fresher copy of the page contents than about when the page "expires", per se, but I think you could utilize it, especially if you remember to remove the event pages or change them once the event has transpired.

There's another possibility too, if you just care about Google and figure that no-one who wants to come to your event would use Yahoo or MSN Search: "Unavailable_after". Just recently, Google's bloggers wrote about it, actually, as you can read in their confusingly named blog entry: robot exclusion protocol.

The gist of their message is that you can use the following:

According to Google, this will actually delete the page from the Google index on the specified date and time, so even if the page continues to exist on the Web site, it won't be findable from a Google search.

Frankly, the former solution is mediocre and the latter solution is goofy because it's Google-specific, but those are really the only two suggestions I have, other than to be strict about having a Web site that has no information about past events or recycles pages so that your Halloween party information page always has future information on the top and previous event information below it.

Hmmm... that might be the smartest solution, actually. Imagine you have a page on your site for "halloween-party.html" and the first paragraph is always about the next event, whether it's two weeks or fifty weeks in the future, while the rest of the page offers up highlights of the previous party or parties, including pictures, commentary, and amusing anecdotes.

The only place that might break down is with concerts or lectures listed by band name or speaker. You might never have the Hip Hop Cantor perform again at your temple, but I think this basic approach would still work: the information page would be future focused before the, uh, concert, then discuss the event after the fact once the concert was completed.

Hope those give you some ideas and spark your creative juices (or some such mixed metaphor like that). Good luck to you!