When you follow a link from search engines etc. you see the Hello World box on the right if you are an unregistered user.
Why does not this same block show on Stackoverflow homepage for the same purposes? Is it a SEO consideration?
We will be replacing this box with something a little prettier and more front and center. It will be dismissible into a thin horizontal strip across the top of the page.
If you haven't noticed, we have also removed a lot of cruft in the right sidebar for anonymous users.
Our intention is to focus more on what is relevant instead of throwing everything at users and hoping something sticks.