when a page changes

[lucy24]

I'm really trying to avoid putting this in a Google forum, because it's a general question about any and all search engines.

Premise: Search engines like "fresh content" blahblah. Keep updating your pages and they'll like you.

Question: How do they tell?

There's the bottom-line 304 response, but that's meaningless for most pages on most sites. I checked my logs; the last time I recorded a 304 on a page request was a couple of years ago. I'm pretty sure it coincides with when I started including php-generated navigation: once you've got dynamically generated content, a 304 can't be sent. The only recent 304 I could find was in requests for "quickstart.html", my host's placeholder page for new sites that haven't got any content yet. That's pure html.

The Googlebot (rarely) and the Seznambot (always, I think) send the "If-Modified-Since" header. But, again, meaningless if you've got dynamic content.

So ... what counts as a change? Is there a whole vast section of the respective search engines' computers devoted solely to comparing this week's version with last week's version? If you swap two paragraphs, is that perceived as a substantive change, or no different from replacing one word? If you're not using a standard CMS with known <div> names, do they recognize that suchandsuch link-- which wasn't there last week-- is just your internal navigation, nothing to do with page content?

And what about stylesheets? If there's no change in content, but everything looks different-- obvious example, if you've added something to your global css to make the site responsive-- is that a change?

[Andy Langton]

I think the premise can be disputed, on a couple of counts. The "fresh content" idea is as much about *new* content as keeping older content updated. Secondly, I've never really bought into the idea in general. Of course, there are certain searches which demand recency, and if you're targeting those then you need to be new. But I've never seen anything that suggested that an updated old page outperforms an old page in terms of it being a direct algorithmic factor. Or if it is, the effect is very small.

As to what counts as a change, for Google, at least, you can get the date in results to change just by changing a date on the page. However, there is definitely a more complex analysis. For instance, if you do a date-restricted site: search, you will see significantly changed pages show up alongside completely new ones. For instance:

site:webmasterworld.com (tbs=qdr:d) [google.co.uk]

Notice the time reference for the homepage. The whole page didn't change, of course. Swapping a few words around will not cause this effect, nor will, for instance, changing the page title. Visual changes don't seem to make any difference, either.

[keyplyr]

The server includes a 'last changed' time-stamp in the document request response so the bot can tell (if config'd to read that field.) Whether Google or other SEs see that as an update probably depends on things Andy indicated.

[tangor]

Minor change (look, feel, css) might be major for the user but means nothing to the SE as the content did not change. Changing whole paragraphs might be a change DOWN THE LINE. Removal and/or Replacement of a page is a change that can be codified immediately. Determining what is a "change" that an se will notice is an intriguing question.