Did this just start recently? It's easy to accidentally change the zoom level on a page. To reset zoom to the default (set by the site, usually), you can use Ctrl+0 (that's a zero) or

View menu > Zoom > Reset

More info on the zoom feature: Font size and zoom - increase the size of web pages.

Does that help?

This problem is not a zoom or font size problem. Zoom (using clt and mouse wheel) increase that which is in the page. My problem is that the page itself is in the middle of the screen leaving several inches on each side of the web page. I only began using Firefox this month and it seem odd. I don't have this problem in IE.

Could you give the URL of a site that has this problem (assuming no login is required)?

And/or could you post a screen shot showing the blank area that zoom won't fill? This article might help: How do I create a screenshot of my problem?

Firefox doesn't zoom in on a page to fill the screen (fit to width).

You can use an extension to set a default font size and page zoom on web pages.

• Default FullZoom Level: https://addons.mozilla.org/firefox/addon/default-fullzoom-level/