This infection is a Java script based insertion from the Smitfraud family. Make sure that your Java is kept up to date to prevent vulnerabilities, consider using Firefox with NoScript for your browser.
Malwarebytes free version should remove it. Download it here
http://download.cnet.com/Malwarebytes-Anti-Malware/3000-8022_4-10804572.html
Download, install, update and run a full scan.