Here is a screenshot of what my new tab page looks like. Thanks for any help you may offer.

Firefox automatically adjusts the number of columns that fit on the about:newtab page if you adjust the width of the Firefox window or zoom the page in or out and no longer resizes the thumbnails. The current release doesn't resize the thumbnails, but instead reduces the number of tiles to fit the current screen width, so you may not see the number of columns that is specified via the browser.newtabpage.columns pref. Zoom out the about:newtab page to see more tiles. Make sure that you have only one tab with the about:newtab page open.

See also this extension:

• New Tab Tools: https://addons.mozilla.org/firefox/addon/new-tab-tools/

Thanks for so much for taking time to review my problem and to respond. I understand what you say about the resizing options, but before this change my thumbnails were not blurry when all nine were on the new tab page. Since the change, they have been blurry. Maybe there is no fix for this now, but hopefully the next version will change it back to the way it was when the tiles were not blurry.