From now on, Google will give you a warning notice, if search results you want to view contain a malicious code.
The sign “Warning – the site you are about to visit may harm your computer!” will appear, when you click on a link leading to a site that might install spyware and adware to your machine. The warning goes along with suggestions to pick another web site up from results or to try another search. Suspicious sites are not blocked by Google, after you view an alert; you can choose to continue browsing potentially harmful web pages.
A list of dangerous web sites is apparently provided by StopBadware.org as they are boosted by Google as a source where you can learn more about malware. StopBadware.org home page informs about cooperation and promises to create an individual report for all sites marked as malicious.
Enjoy safe browsing!