css selector if more than one of same type code example

Example 1: css multiple classes

//HTML Code
<div class = 'firstClass secondClass'></div>

//CSS Code
.firstClass.secondClass {
  
}

Example 2: select two stuffes css

#load p,
#load h1,
#load h2,
#load h3,
#load h4,
#load h5,
#load h6 {
  font-size: 80%;
  margin:2%;
}