unable to go to www.avast.com

[ARULKRISHNA]

Hi members
  I am not able to go to antivirus websites www.avast.com in my browser like firefox, IE, chrome,but able to update virus definitions.I am using avast free edition. How to remove the malware/spyware. After Full scan also facing same problem.

[Pondus]

Check for malware with this

Malwarebytes Anti-Malware 1.51. http://filehippo.com/download_malwarebytes_anti_malware/
always make sure the program is updated before you scan
click on the remove selected  button to quarantine anything found

post the scan log here

[bobo1]

Def a trojan redirector malware as blocking antivirus sites. Check windows host file for extra entrys

[DavidR]

HOSTS file redirect a common malware tactic to block AV sites making it difficult to remove malware - 127.0.0.1 check your HOSTS file using notepad or a text editor of your choice, C:\WINDOWS\system32\drivers\etc\hosts or do a search for HOSTS to find it if not there.
 
Once open you are looking for entries with avast.com on the line, you may well see other AV sites, post the contents of the hosts file. http://en.wikipedia.org/wiki/Hosts_file