This is a rotating sign for a foot clinic in Los Angeles. If the happy foot is facing you when you see it, you will have a good day. But a sad foot means you will experience bad luck.
Kelly Coyne of Homegrown Evolution has more:
The podiatrist's sign above marks the entrance to our neighborhood. It charmed us the first time we saw it: It's a foot — with feet! And we immediately named it the Happy Foot/Sad Foot sign. Soon we learned that other people called it The Happy Foot/Sad Foot Sign as well. The name seemed predestined and universally applied, and it was recognizable enough that we could pinpoint our location off of Sunset Blvd. by saying, "You know the Happy Foot/Sad Foot sign?"
The Foot rotates slowly, unless it's broken, which it often is of late. But when it's rotating, you are always tempted to check out which side is facing you when you first come into sight of it. A happy, smiling foot is portends a good day, or at least a general thumbs up from the universe. We've always thought so, and come to find out, many other people also practice this form of primitive divination.
It's even immortalized in fiction. Our friend, Anne, resident of this same 'hood, tipped us off that The Foot is featured in You Don't Love Me Yet by Jonathan Lethem (2008):
Lucinda's view took in a three quarter's slice of the sign as it turned in its vigil over Sunset Boulevard: happy foot and sad foot suspended in dialog forever. The two images presented not so much a one-or-the-other choice as an eternal marriage of opposites, the emblem of some ancient foot-based philosophical system. This was Lucinda's oracle: once glance to pick out the sad or happy foot, and a coin was flipped, to legislate any decision she'd delegated to the foot god.
A quick Google search shows the Foot is acknowledged (it shows up in Flickr sets and odd comments here and there) but not famous, outside this locale. However, I was delighted to find an animation called Happy Foot vs. Sad Foot. Instead of seeing the Foot as a marriage of opposites, as Lethem does, the animator portrays the Feet as two characters engaged in an endless, existential binary feud. For Sad Foot, life will always suck, while Happy Foot will always gets his way. (Note in the comments for this animation that someone steps forward claiming to be the designer of the sign's graphics.)
Read the rest of Kelly's essay: Our Happy Foot / Sad Foot Sign