Reset the page zoom on pages that cause problems: View > Zoom > Reset (Ctrl+0 (zero); Cmd+0 on Mac)

• http://kb.mozillazine.org/Zoom_text_of_web_pages

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/
• NoSquint: https://addons.mozilla.org/firefox/addon/nosquint/

At least in my version of Firefox 8.0, the View menu no longer exists. Single, orange Firefox dropdown menu in the upper left corner. Menu options with further selections include Print, Web Developer, Bookmarks, History, Options, and Help. None of these menu items include View or Zoom.

Press F10 or tap the Alt key to bring up the "Menu Bar" temporarily if the Menu Bar is hidden.

See also:

• https://support.mozilla.com/kb/Menu+bar+is+missing