For the love of God, I’ve looked at so many tutorials on how to line up two boxes with CSS, and none of them seem to work for my neocities site. What am I doing wrong?

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

#plate {
  height: 100%;
  width: 750px;
  margin: 10px auto;
}

.sidebar {
  border-radius: 25px;
  background: rgba(214, 245, 245, 0.7);
  text-align: center;
  align-items: center;
  
  float: left;
  width: 30%;
  
  border: 15px;
  padding: 10px; 
}

.meat {
  border-radius: 25px;
  background: rgba(242, 217, 230, 0.7);
  
  float: left;
  width: 90%;
  
  margin: 10px;
  border: 15px;
  padding: 10px;
 }