There’s a glitch with this offer I received today.
Clicking the circled ‘x’ in the top-right area doesn’t close the page. It takes you to your Shopping Cart in the Avast Store. :
Yes seems awkward, however 1 year of Pro protection for $20 Bucks is a good price/value! 
I have had that offer a couple of times, on my XP Pro and win7 systems and both closed successfully using the X.
Not sure why yours didn’t, I just wonder if the whole window, with the exception of the X is an activation, if so you would have to be pretty accurate with the mouse cursor.
I’ve run into that several places, where if you’re not dead-on the X when you click, it’s read as clicking inside the window instead, with predictable results. Not much fun for those of us with less than perfect eye-hand coordination, or with hands that aren’t rock-steady.
For some reason it seems to occur more frequently (for me) in 7 than it did under XP … I’d guess the default settings for the mouse drivers have changed.
Follow up
1/. Guess what! The 60% discount has today grown to 70%. (Lucky I didn’t accept the first one!)
2/. The price is good. The problem for me is that I already have more valid AIS licenses that I can’t fully utilize due to incompatibility of some of its components with the OS and hardware of the machines.
3/. The ‘x’ doesn’t work in any conventional manner. Hovering over it changes it from a pointer to a hand but clicking always takes you to the shopping cart no matter how precise you are at locating it.
I don’t know if the fact that I don’t have the avast store as an option in the avastUI (I unchecked that option a long time ago), so I don’t if that might have an impact in not being able to open the shopping cart. Though that said, I have clicked some other options/offers to capture images and that worked taking me to a cart of sorts within the UI.
Currently I have silent/gaming mode enabled, so I’m not getting any popups or offers, etc.