I hear once you've worked there for 256 days they teach you the secret of levitation.
Many look up to Google as the ultimate workplace in the IT industry. Therefore, they have lots of applicants but can afford to be very selective, and only the best and brightest succeed.
In the first panel, the guy at the computer asks his friend (both look like Cueball) what he thinks about working at Google HQ (Head Quarters). His friend starts out by dismissing Google as a "corporate idea factory," but from the rest of his speech, we can infer that these are not his true feelings. He is exhibiting the attitude known as "sour grapes," where you criticize something that is out of your reach, or that has been denied from you.
In the last panel, it is revealed that the friend has been trying very hard to get a job at Google, even resorting to bribing the interview panel by baking them a cake "shaped like the Internet." This misguided action is a sign of how much he wanted a position.
Since the Internet does not have a defined shape, it is difficult to visualize exactly what he baked. The comment was maybe foreshadowing 195: Map of the Internet that came out a week later. It would, though, be a more interesting cake if it looked like the map in 256: Online Communities, but that came out 20 weeks later. Another possibility is that the comment is a reference to this video, in which the black box shown is supposedly the Internet. If this is the case, then the cake would have been shaped like the box in the video.
The title text says that if you work for Google for 256 (28) days, you get to learn how to levitate. This displays some of the mystique with which Google is commonly viewed. The joke here is that 256 is bigger by one than the largest value a single byte can hold, as has been demonstrated with the 256 Bug. However, Astro Teller, the director of Google X labs, a Google division that researches "moonshot" projects, has mentioned in an interview that they contemplated starting a levitation project.