What does 4/20 mean???

To be fair, it seems like no one really knows the story behind how 4/20 originated. According to the Internet's most trusted source for Internet slang, uh, Internetslang.com, 420 quite simply translates to "weed." One popular urban legend maintains that the term originated because there are 420 chemical compounds found in cannabis, while another claims it was a secret police code used to indicate the presence of marijuana.