The 37-year-old American was sanctioned for an incident which took place during a practice session before the tournament got underway.
“The code given is for unsportsmanlike behaviour. The reason is court damage,” a spokeswoman told AFP.
Williams is in action twice later Tuesday when she faces fellow American Alison Riske for a place in the semi-finals.
She then returns to Centre Court to partner Britain’s Andy Murray in the mixed doubles.