Today i read about Google Safe Browsing Diagnostic report, and it's really interesting.
Google is providing a security diagnostic report about web sites, where they give:
*What is the current listing status for [the site in question]?We display the current listing status of a site and also information on how often a site or parts of it were listed in the past.*What happened when Google visited this site?This section includes information on when we analyzed the page, when it was last malicious, what kind of malware we encountered and so fourth. To help web masters clean up their site, we also provide information about the sites that were serving malicious software to users and which sites might have served as intermediaries.*Has this site acted as an intermediary resulting in further distribution of malware?Here we provide information if this site has facilitated the distribution of malicious software in the past. This could be an advertising network or statistics site that accidentally participated in the distribution of malicious software.*Has this site hosted malware?Here we provide information if the the site has hosted malicious software in the past. We also provide information on the victim sites that initiated the distribution of malicious software.
This service is very useful and is similar to McAfee Site Advisor, you can check an example report for doubleclick.net here where in the past malware was detected.
This report is what google knows about the security of a site, better said the potential security risks that you can find in a site.
You can access this service via the website, or via Firefox "additional information"
More information in the Google blog