Robert_Charlton - 10:40 pm on May 21, 2013 (gmt 0)
PS: Frost_Angel - As I posted in another thread where a member was similarly panicked, I would just chill out for a while.
404 errors are reported to alert you that requests for the urls are showing errors. If for some reason you were getting errors on pages that you assumed were in the index, then you should be concerned.
In this case, the errors for pages that have been removed are expected behavior. I'd watch with interest the history as it unfolds in Google, as it might give you some flashes of insight, but... considering current circumstances and that you are not alone... I certainly wouldn't lose any sleep over what you're seeing.
Here's the nwelsh post in full, as I think it might be helpful to calm you. Notice the numbers he's seeing... and that he doesn't seem to be worried by them....
It's an old data set, our site has over 500,000 pages and the URLs showing up in the index right now are pages we had removed from our site after first version of panda/penguin hit.
I believe this is the pattern:
Reset data to old
Reindex the web
Unleash the new algorithm on the new index
Could be 100% wrong, but believe this is what's happening.