Thanks to Sara, there is a very easy way to add code to your site to protest against SOPA:

Drop the following code in between your two tags on your site, your users will be redirected to the blackout page that describes what you are doing and why.

<br /> <script><br /> window.location = "";<br /> </script>

Then, when the protest is over, simply remove the added code. The protest is starting at 12am on 118, and lasts 24 hours.