Please ‘modify’ your post change the URL from http to hXXp, as you did with the first URL (but not the infection details) to break the link and avoid accidental exposure to suspect sites, thanks.
There is an on-line contact form, http://www.avast.com/contact-form.php?loadStyles for: * Sales inquiries; Technical issues; Website issues; Report false virus alert in file; Report false virus alert on website; Undetected Malware; Press (Media), issues.
If you are reporting an FP, then you get another input field open, click Browse button and navigate to the file or enter the web URL for the site you wish to submit for review (Network Shield), etc. A link to this topic also wouldn’t hurt.