• You are in Private Browsing mode if you see "Tools > Stop Private Browsing", possibly grayed
• You enter Private Browsing mode if you select: Firefox > Preferences > Privacy > History: Firefox will: "Never Remember History"
• To see all History settings, choose: Firefox > Preferences > Privacy, choose the setting Firefox will: Use custom settings for history
• Uncheck: [ ] "Automatically start Firefox in a private browsing session"

See also:

• Always start Firefox in a private browsing session

Firefox did not always automatically start in private browsing mode.

However i have followed your advice and, finding the item checked, unchecked it. Thanks.

That leaves on question.

"on several websites, such as ESPN and others, the print on one line overlaps the print on the next line and the print on the lower line cannot be read "

Any thoughts?

Reset the page zoom on websites that look wrong: "View > Zoom > Reset" (Ctrl + 0 (zero))

If you increased the minimum font size then try a lower setting (default is none) as a too high value can cause issues like you described.

Tools > Options > Content : Fonts & Colors: Advanced > Minimum Font Size
Tools > Options > Content : Fonts & Colors: Advanced > "Allow pages to choose their own fonts, instead of my selections above"

See http://kb.mozillazine.org/Zoom_text_of_web_pages See Websites look wrong or appear differently than they should and Change the fonts and colors websites use

Menu differences: Windows: Tools > Options - Mac: Firefox > Preferences - Linux: Edit > Preferences

the "view>zoom>reset" step did nothing.

On my Firefox there is no "option" under "tool" thus i could not work with the second recommendation.

I had the same problem! I went into the "Tool" menu-bar and clicked "Options", then in the "Firefox will" box scroll to the "Use Custom setting for History" then click it. Then un-check the "Automatically Start Firefox in the Private mode" button and then click "ok." You should be ok then. The "Private Browsing" and the "Clear History" buttons are unlocked.