https://stackoverflow.com/questions/4016067/whats-a-3d-doing-in-this-html https://stackoverflow.com/questions/4016067/whats-a-3d-doing... Basically: it's a for

https://stackoverflow.com/questions/4016067/whats-a-3d-doing-in-this-html https://stackoverflow.com/questions/4016067/whats-a-3d-doing... Basically: it's a form of escaping, and like other forms of escaping the escape character itself has to be represented as an escape sequence. So in other languages where \ is the escape character, you have to put \\ to represent an actual slash rather than the start of an escape sequence. Here = is the escape character followed by the hex of the character, so to represent a literal = it needs its own hex value 3D after it.