It is supposed indicate that you already have the page open and by clicking on it take you there. It does not apply to the current tab.

• https://www.mozilla.com/en-US/firefox/features/#feature-switch
• http://kb.mozillazine.org/Location_Bar_search
• item #32 shows variant in how shown if you have oldbar extension

  http://dmcritchie.mvps.org/firefox/firefox-problems.htm#fx4ext

Ok, but I don't have those tabs even open. For example, I might have my e-mail website up and nothing else, and it still says to "switch to tab."

It is possible that there is a problem with the files sessionstore.js and sessionstore.bak in the Firefox Profile Folder.

Delete the files sessionstore.js and sessionstore.bak in the Firefox Profile Folder.

• Help > Troubleshooting Information > Profile Directory: Open Containing Folder
• http://kb.mozillazine.org/Profile_folder_-_Firefox
• http://kb.mozillazine.org/sessionstore.js

If you see files sessionstore-##.js with a number in the left part of the name like sessionstore-1.js then delete those as well.
Deleting sessionstore.js will cause App Tabs and Tab Groups and all open tabs to get lost, so you will have to create them again (make a note or bookmark them).

See:

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

Do you mean you email is on the only open Firefox window, or is the only tab open in the current window. The scope applies to all of your tabs except the current active tab, and it is limited to the visible viewing level of each tab open in current and in other open windows.

You know how the AwesomeBar search works - you can type in parts of word (strings) etc of anything in the title or the url of your bookmarks or history. Try a similar search for tabs type in those strings and include % (percent sign) space delimited anywhere at beginning end or end or in-between.