problem

That is an AD, short for "advertisement", which is NOT a virus.
Look here to prevent further popups.
Maybe the section titled "Why am I being redirected to other sites?" in the following FAQ can help?

Currently there are zero viruses affecting Mac OS X in public circulation, but there are other kinds of malware existing, that can infect your Mac.
But as long as you don't install software from unknown and untrusted sources, you are safe, as malware needs administrative permissions to run successfully, which means, you need to install the malware yourself, it can't install itself (one of the reasons, why a Mac OS X virus hasn't appeared yet).
To learn more about malware in Mac OS X and what steps can be taken to protect yourself, read the following F.A.Q.:

Mac Virus/Malware Info by GGJstudios
The above F.A.Q. includes the following topics:

• Malware terminology - What is the difference between viruses, worms, and Trojans?
• Antivirus apps
• What security steps should I take?
• What about sending files to Windows users?
• Why am I being redirected to other sites?
• Recent threats in the news

​

To learn more about Mac OS X: Helpful Information for Any Mac User by GGJstudios​

"How to maximise your MacRumors troubleshooting experience" created by mad jew in 2006​

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