Through his Twitter feed, Matt Cutts, head of the webspam team at Google, announced an update to the Page Layout algorithm via one of his "weather reports". Google first introduced the Page Layout algorithm in January of this year. Its purpose? To reward sites who favoured content over ads above the fold.
In their January announcement, Google said, "If you click on a website and the part of the website you see first either doesn't have a lot of visible content above-the-fold or dedicates a large fraction of the site's initial screen real estate to ads, that's not a very good user experience. Such sites may not rank as highly going forward."
The original Page Layout algorithm affected around 1% of searches globally. This update is set to affect approximately 0.7% of English queries.
In a follow-up tweet, Matt Cutts also pointed out that this update is not related the much talked about Panda and Penguin algorithm changes, nor the recently announced Exact Match Domain update.