Does this message only appear on the "old" Firefox start page?

http://www.google.com/firefox?client=firefox-a&rls=org.mozilla:en-US:official

Once Firefox 4 was released, that page was no longer updated and it does not check your version dynamically.

If the message appears in a pop-up or in an ad on other pages, they may be inducements to install malware. You should check that you do not have any add-ons causing this problem. Either:

• Ctrl+Shift+a
• "3-bar" menu button (or Tools menu) > Add-ons

In the left column, click Extensions. I suggest disabling everything unknown or nonessential to see whether that helps reduce the messages.

no nothing like that it's just that if i'm doing something and it refreshes the page it says the browser is out of date and wants me to update it but i don't need to

Suspicious. Definitely check the add-ons, and consider some supplemental security scans. This support article lists free tools other Firefox users have found helpful: Troubleshoot Firefox issues caused by malware.

If you get a pop-up message asking to update Firefox or plugins then such a message is likely a scam and you should never respond to such an alert to avoid getting infected with malware.

• Only update Firefox via "Help > About" or by downloading and installing Firefox from the Mozilla server and never via a pop-up or link on a web page.
• Plugins should only be updated via the plugin itself or by visiting the home page of the plugin.

Do a malware check with several malware scanning programs on the Windows computer. Please scan with all programs because each program detects different malware. All these programs have free versions.

Make sure that you update each program to get the latest version of their databases before doing a scan.

• Malwarebytes' Anti-Malware:
  http://www.malwarebytes.org/mbam.php
• AdwCleaner:
  http://www.bleepingcomputer.com/download/adwcleaner/
  http://www.softpedia.com/get/Antivirus/Removal-Tools/AdwCleaner.shtml
• SuperAntispyware:
  http://www.superantispyware.com/
• Microsoft Safety Scanner:
  http://www.microsoft.com/security/scanner/en-us/default.aspx
• Windows Defender:
  http://windows.microsoft.com/en-us/windows/using-defender
• Spybot Search & Destroy:
  http://www.safer-networking.org/en/index.html
• Kasperky Free Security Scan:
  http://www.kaspersky.com/security-scan

You can also do a check for a rootkit infection with TDSSKiller.

• Anti-rootkit utility TDSSKiller:
  http://support.kaspersky.com/5350?el=88446

See also:

• "Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked