COM3 not working

it shows this whenever i use it:
on any project with serial monitor.
can some one explain?
im mad
maybe try on your board.
link to project:
heres the code:

#include <IRremote.h>

const int RECV_PIN = 7;
IRrecv irrecv(RECV_PIN);
decode_results results;

void setup(){

void loop(){
  if (irrecv.decode(&results)){
        Serial.println(results.value, HEX);

Nonsense characters printed to serial indicates a baud rate mismatch. Do you have your serial monitor set to the same baud rate as your sketch?

What board is it?