My virus scanner warns me that the site has mallware on this url (probably a banner):

http://m.addthisedge.com/live/t00/250lo.gif?jwegg1%26uid

Yeah, everywhere I go on chess.com it pops up.

In what way does Avast think it is "harmful"?

I use Adblock Plus as well, but I still get the notification. You might want to run for your life screaming.

Which page are you seeing the warning on?

Which avg program are you using?

I tried viewing the link you posted, just shows as a complete black page to me sorry.

I got the same message to but it stopped notifing me.

I installed the freebie version of Avast and so far haven't had any warnings on either Chrome or Firefox on Chess.com

I use Avast and am using Chrome and I havent had any problems as yet.

I'm using the free version of avast and I have got this warning as well. I'm using Firefox browser.

Fwiw  - I use "hosts" (rather than Adblock Plus).  It blocks addthis trackers and a ton more.

Still use ghostery, but probably don't need to.

http://winhelp2002.mvps.org/hosts.htm

Don't tell my girlfriend there's mallware here. She'll want to shop and I'll have no time for chess.

I've never had any virus warnings here.

http://toolbar.netcraft.com/site_report?url=http://www.chess.com

Nothing wrong here. 0/10 risk rating (not that I know what risk it's referring to).

Don't be so ridiculous

AVG doesn't report a virus for chess.com but did say something about Lady Gaga.