Today my browser opened this page: http://aos.avast.com/upgrade/1006
Is this a real avast page? Someone please help!
Edit: I tried to check if aos.avast.com was a site, but it said "URI mismatch /‘’ is this a virus or what??
Yes thats a real Avast page for Avast Online Security. 
Alright, thanks! And it’s right that aos.avast.com is not an existing site? So I shouldn’t worry about viruses? (:
The aos. indicates that it is a sub-domain to avast.com, so the only way you would be able to access it is if it was avast doing the accessing, e.g. it is accessing a specific link.
Unlike normal domains or sub-domains which have a home page, like index.php (which you could access), these sub-domains ordinarily the user can’t directly access them.