follow this guide and attach (not copy and paste) the requested logs http://forum.avast.com/index.php?topic=53253.0

1. AdwCleaner
2. Malwarebytes
3. OTL
4. aswMBR

when done the removal experts will be notified. It may take hours before they arrive so be patient

I ask this because it's only my site that gets this message and no other that I've visited.
OBS....what is Your website URL