So what does it mean?
"From the top down, the message contains binary image representations of the numbers one through 10, atomic numbers of the five elements essential to life on Earth, the chemical formula of the DNA molecule, the numbers for the average human height and the number of the world's human population in 1974, as well as images of the human form, the solar system (with Earth displaced to indicate it is the planet from which the signal originated), and the transmitting radio telescope, with its diameter indicated."
(http://seti.planetary.org/seti-messages-arecibo.html)