If your website is marked as “This site may harm your computer” by Google, most likely your site is hacked. In that case, log in to Google Webmaster Tools and it will shows you which URLs are “infected”. This should help a lot to clean the malware.
So make sure you have configured Google Webmaster Tools for your live websites.
The most common form of malware could be found in the following locations
Follow the URL below and clean all the malware, then you can request Google to review the website at Google Webmaster Tools.