That is a 3rd party advert
and not the Download.com option to download Avast Free version.
Advertising is done through Google Syndication advertising and CNET has no control over that. However I have alerted the Forum Manager to your post above so he can forward this on to the correct people.
May I offer a suggestion to help you avoid these traps in the future. If you use Internet Explorer change it to Firefox for which you can install the AdBlockPlus add-on. It removes all advertising from web sites.
In the Download.com link you gave above I don't see those adverts because of ABP. I have learned the hard way never to trust web site advertising.
I hope that helps.