Contact the webmaster. It is not avast! that has the malicious code, but the site.
See: http://forum.avast.com/index.php?topic=100037.msg799079#msg799079
Suspicious appendChild iframe.
Please ‘modify’ your post change the URL from http to hXXp or www to wXw, as I have in the quoted text to break the link and avoid accidental exposure to suspect sites, thanks.
That is your choice on the exclusion, but the correction as !Donovan stated needs to come from the web master. Just look at !Donovan’s image of the suspect code in Reply #14 and later post by polonus.
The user is ill advised to close down the shields when access to a site is being blocked. The shield detection is generally very accurate,
polonus