Cookies will be enabled already otherwise you wouldn't be able to post on this forum.

The problem is most likely caused by a piece of Adware which you have installed called My Web Search.

To disable it, click the orange Firefox button, go to Add-ons, then Plugins. Find it in the list and then click the "Disable" button. If there's a Remove button, that would be even better so that you can remove it from Firefox, but that probably isn't the case.

I notice too that some of your other plugins are seriously out of date which exposes your system to attack. Please visit the Plugins Check page and update where necessary.

See:

• https://support.mozilla.com/kb/Cookies
• https://support.mozilla.com/kb/Enabling+and+disabling+cookies

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

Incidentally, if you have an Add-on installed which manages cookies, then that could also be the culprit.

• You can test it by clicking Help | Restart with Add-ons disabled.
  
  
• In the next menu, click the button which says "Continue without making changes".
  
  
• Then go to the site where you normally see the error message. If it doesn't appear, then the problem is being caused by one of your Add-ons. See this article for instructions on how to proceed further in that particular case: Diagnose Firefox issues using Troubleshoot Mode