Google, Wikipedia and a host of other websites are either going dark or making huge, unmistakable statements on their homepages in protest. The new laws proposed by US legislators, the Stop Online Piracy Act and Protect IP Act, have been attracting a very negative reaction from the web community over the past couple of months, which is today culminating in a day of protests. Aiming to curtail copyright infringement on the web by giving the US government unprecedented new powers, both SOPA and PIPA have been rejected by some as overreaching and unhelpful laws that cannot coexist with a free and open internet.
A technical breakdown of this can be found here at reddit if you would like to learn more.