There are cases where you do not want to be in google’s index. For instance if you have an old webpage that has been replaced by a new webpage, but the old one comes up higher in google’s results.
Or if you have a phone number listed in google’s phone lookup and don’t want it to be listed on the search engine.
If you have an old website location or URL that you replaced with a new one or you have a second webpage that points to your other webpage google prefers it if you do a 301 permanent redirect on the old website.
If you don’t want a certain page to show up in google’s cache, if you take it down, it will instantly disappear, you can tell google not to cache your webpage.
ex: META NAME=”googlebot” content=”noarchive” in the HEAD section of the HTML files.
If you have a page that is already in the cache, you can request it be removed from google’s index, or a quick and dirty workaround is to replace your cached page with a blank page (on the same server with the same title) and the next time google spiders your page it will update the cache of that page by removing all previous text on it.