The first message sent over the internet was just the word "LO".
Why it is true
The original message was supposed to be "LOGIN", but the ARPANET system crashed after the transmission of the first two letters, leaving the historical record incomplete.
Source: Network History
Would you rather be asked first?
This is the reading side of the site, so the answer is in the sentence above — that is the whole point of it. Test yourself works the other way round: the question comes on its own, and the fact and the explanation only appear once you have answered.