Although I see the code in my header, my Google Analytics account page says the code is not active on my site. I'm getting the yellow warning symbol there.
These instructions in the GA plugin settings indicate I can confirm tracking by checking the code with Firebug:
If you want to confirm that tracking on your blog is working as it should, enable this option and check the console in Firebug (for Firefox)
Check the code where? From the front page of my site? From the GA admin page? Where, Yoast? Firebug is for checking html and css. How is it supposed to confirm that GA is active, anyway?