This is your anti-virus stopping you from going to a phishing site (as reported by Avast)

bb,

Thank you. Any idea why I'm being redirected to there when I use a Houzz link, or, more importantly, not get redirected there in the first place?

You probably have some kind of malware on your computer that slipped past Norton. Looks like the malware is redirecting your browser to a page that Norton doesn't like and blocks. No idea why you're only being redirected while browsing Houzz. Usually trouble like this starts after installing a questionable program or browser extension. You might be able to remove it just by uninstalling the questionable whatever that was installed. Also, you can try downloading and installing the free version of Malwarebytes. I've had good results with that program. I'd install it, close all programs, disable Norton, then run a scan with Malwarebytes. After you've removed the trouble maker you might still need to reset your browser settings to default. After your computer is cleaned up you can uninstall Malwarebytes and switch Norton back on if it doesn't automatically switch on.

"Fortunately Norton has blocked it each time."

I'm not a Windows person but I'm curious.

If Norton catches it and blocks it, does it offer to remove it?

Richard, it doesn't consider it that type of threat. Just blocking it is enough.