Google Give Searchers 'Instant Previews' of Result Pages
First pressing 'Enter' was to much work... now actually clicking on the links and visiting the sites is to much, too... Google is testing instant previews, where you can see a miniature rendered view of the landing page without requiring you to click through and back-arrow.
Well it's very easy to turn it off, just click the settings link at the top of the page.
The drop down also does not obscure any of the page, it pushes it down.
If you don't want to use new helpful Google features, you have the option to opt out of them, but Google does a significant amount of testing on their pages for usability so I'm sure most people will find these features helpful.
For a few billion popular Web pages, Google will store the images of the pages. For others, it will generate the preview on the fly, in less than one-tenth of a second, Mr. Krishnan said.
source: http://bits.blogs.nytimes.com/2010/11/09/google-introduces-visual-previews-of-search-results/