Not about 1999. Not 1999 before compression, or after it. The HTML your browser was handed to draw this is 1999 bytes long, and you do not have to believe that:
curl -s https://1999loc.com/1999 | wc -c
The obvious version of this joke was to make the site itself 1999 lines of code. That number cannot be kept. It moves every time anything is built or a comment is rewritten, and a number you can only hold by never working again is not worth holding. The length of one page, though, is a thing that can be true forever.
There is no padding in here. No run of spaces, no filler comment cut to size. Every byte is a byte of this page, so changing a sentence costs an equal change to another one. A test counts the bytes on every build and refuses anything else, which means the only way this page is still exactly 1999 bytes is that somebody kept paying for it.
There is a second one, and it costs nothing to keep. The standings carry a board ranked by how close a repository's line count lands to 1999. It always has a winner, because nearest is a question that always has an answer, and so far nobody has hit it exactly. Land on it and nothing can beat you, because nothing beats zero.
Which is the trick the rest of the site runs on: do not believe us, go take the measurement.