Don is noticing a lot of underlined and linked words that trigger pop-ups on his website. There are some sites that will underline keywords that trigger pop-up ads when the pointer moves on top of it. However, Leo says if he's seeing it on his own site, then it's malware and it's probably doing even worse. Leo says to make sure his OS (Windows 7) is updated regularly. It may have come with a download. Leo's opinion though is to back up his data, format the hard drive, and reinstall Windows. That's the only way he can be sure it's clean.
The other school of thought is to try and clean it. He can run a antivirus program or malware scanner like MalwareBytes. He can also run the Microsoft Malicious Software Removal Tool (Click start, select "Run", type "MRT", hit enter) or (Windows key + R).