I have to agree with the comment RE: web master tools keyword searches etc.
For example, over the past month I have had pages say they`re in the top 10 but when you search google they are nowhere to be found... perhaps hundreds of positions later...
I think what Google is doing is sliding back those pages on purpose for some temporary reason, I don`t think it`s due to a mistake or miscalculation in webmaster tools, I think it`s google activating some sort of action on that page...
I`m certain of it...because all those pages had previously done well and then suddenly there is a change in results.
Unless Google spreads those impressions out over different sites... because how could webmaster tools be accurate on one set of keywords and not on another?