Find the Invisible Cow

At some random location in an otherwise-empty web browser window is hidden a cow. The cow cannot be seen -- for you see, it is invisible. However, moving the cursor across the screen will result in the word "cow" being recited at different degrees of intensity -- the closer the cursor drifts to the cow's concealed location, the more fervently the word will be intoned, until finally, the computer practically yelling "COW! COW! COW!" at the player, a click will reveal the hidden animal. Then it hides in a new location and players can try their luck again.