Google is a search engine, not a permanent index.

The actual details of how Google decides to return a particular web page in its results is a closely guarded secret, but a few things are pretty well accepted.

First, Google decides whether to create an index of a site based mostly on how many other sites link to it. Although the number of pages for which indexes are gathered is huge, it's still only a small fraction of the pages on the internet.

Second, Google does not necessarily make a "complete" index of every page. They use an arcane formula (or several) of their own design to determine what they can later "find" on a page that is indexed. The decision probably is based largely on how "popular" a scrap of information is likely to be.

Third, Google apparently sorts the "queries" by popularity. If lots of people are looking for something, the most commonly used "search terms" get priority. This sometimes means that a term less often searched for gets moved out of the system.

Fourth, Google sorts the "hits" by popularity. Once a term has been searched, the position of a particular "hit" in the list of results depends on how many people have clicked on that result. More clicks leads to appearance higher in the list. It's "impressive," I suppose, that Google always reports "100,000,000 results found" for a search; but it will only show you the first 200 or so and there is no way (that I've found) to see the other 99,999,800 results.

When Google has indexed a page, and your search finds a particular result, you cannot rely on always getting the same result in future searches. Google will update its scan of "popular" pages, and will change its indexes for those pages based on what people have clicked in previous results. A song title that few people "clicked" in earlier results can easily get dropped off the index, in favor of something else that more people "expressed an interest" in.

A fifth factor is that a web site that uses "extreme" measures to artificially increase its odds of getting listed in Google may get "black listed" by Google, and all results on the site's pages may be blocked from being displayed in search results. (Most likely this is done by moving its stuff down into the 99,999,800 results one can never see?)

If you come to mudcat, and use the searches on this site, your results should be "permanent" and a search that works once should always work. Mudcat can do something about a song that disappears from its own search machine - probably. But nobody here has any control over what Google reports, and Google's own system is designed to be constantly changing, and to report only the "most popular results."

John