For example, if you go to google.com, you can zoom out as much as you want.
Created attachment 573087 [details] limi.net shows the zooming problem Seeing the same, attaching a screenshot in case it's useful (and I was about to report it separately).
I see this with the nightly start page as well.
bug 701594 landed to fix this.
Closing as a dupe since 701594 is tracking this issue and has more detailed info/discussion.