You're free to serve anywhere, diagonally or straight, from any location. When you serve, the ball cannot fall off the side of the table. It must bounce twice or fall off the end, but not the side. I have no clue who made up this wacky rule, but there's nothing even remotely similar to this in the ITTF handbook.

What is an illegal serve in ping pong?

Hidden serve is the most common illegal serve in table tennis. The player uses his free arm or his body to hide the contact point. It's difficult to see if this was a topspin serve, a no-spin float serve, or a backspin serve. Hidden serve was allowed before but ITTF changed the rule.

Do you get second serve in table tennis?

Each player gets 2 serves, and it alternates until one of the players scores 11 points, unless there is a deuce (10:10). In that case, each player gets only one serve and it alternates until one of the players gets a two point lead.