Whats is up with Google and Firefox?

I've seen some weird things happening today.

I have a website, and I am trying to rank for a keyword related to this website, very competitive keyword.

I ranked on the third page the last few days, been on second page for a like a day the other day.

Anyways, I went to Google now and I typed the keyword and in it came up third on the first page. I was using Firefox.

That looked weird so I went and checked it on Safari. I am 30th on Google when using Safari.

Seocentro.com says I'm ranked 30th as well.

So why is Firefox saying differently?

Clear your cookies and sign out of google if your signed in, google knows what you search for if you've been searching for the same things it remembers what you like

Google applies your history to search results while signed in. In other words; if you sign in your account to check analytics, then head to search and enter your 'widgets' keyword then click on your own site, google thinks this is what you must want to see and gladly gives it to you and only you every time your search for 'widgets'. If you walk over to any other computer, your still in last place...sry.

thanks