Response to oldworzel Rated 5 out of 5 stars
I've never had a an issue with this extension... it's one of the best out there. Perhaps you need to go into its Options and set the Global sizing up. All pages will use the same percent-zoom but if you find an individual page that needs adjusting all you have to do is click on the number/% favicon on the addon bar and it will display a menu for adjusting the size.
I would have to say that maybe 2 out of thousands of pages I've visited needed resizing... all others fit perfectly.