Why is a link considered active, but is no longer on the page?

[MichaelWeisbaum]

How come links sometimes show up in OSE or Yahoo Site Explorer and then when you go to the page, they're not there anymore?  Why is a link indexed or considered active but is no longer on the page?

[SparkplugDigital]

I think Open Site Explorer uses the Linkscape link index which is updated monthly. So it is very possible that the link was taken down or moved to a different page (common with blogs when the link falls off the homepage) since the last time Linkscape was updated.

Another tool I use to check links is SEOHeap which is free and you can quickly check whether a link is active by clicking a button next to the link data.