i think big G's algo had a major update(although it was constantly updating). I've notice many sites were being drop from SERP in a vast number and many of them seems had been penalized by Google resulting in many complains posted in most SEO forums... but until now no proof of them yet..
There has been some major moves around the 4th June from what I'm seeing.
A lot of sites I monitor look like they have been hit by the minus 30-60 penalty and I think it's been sites that (my opinion) have been or are buying blog links etc. Well, going from the Yahoo site explorer research I've done on it, most seem to have a lot of anchor text links buried in 100-300 word review type posts.
Do anyone here notice a big changes on the SERP? if you try to search for a certain KW, Google will only display 600-700 result or even below that which was before we all know that by default, Google shows 1000 result....
welcome to the data centers "now here" "later gone" dancing. oh it's mid year when Google is at it's busiest, lot of my KW have gotten the worst of penalties like the -300 and the -900 lol. lucky though I got at least a hundred sets and those that were taking ages to rank for suddenly made it to Top 15's.
Spamming links is one cause I noticed, sites that acquire too much link love in less than a month seems to be hit hard from me.
I happened to experience fluctuations for my client's website last week with ranking drops from page 1 to no where! I posted a thread relating to this problem. The site is back thank God and it seems Google is going through an updated.
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A wmw thread also points to these changes on the UK front:
yes, same here, some of my keywords dropped then returned back and I just hate that coz it makes me nervous. But of course I know that the fluctuations are normal and the best advise is don't panic and continue working.