Reason for CSS block with no code in?

Question

I'm currently optimising a website's code, the programmer who developed it isn't here.

There is a CSS file with around 1000 lines of code, in this file, there are many blocks with no code inside the curly braces.

For example:

.header{
}

Is there a reason to keep these? Or are they completely useless?

Answer 1

.header{
}
.header .menu_div{
  background : black;
  color:white;
}

<div class="header">
  <div class="menu_div">Menu Div</div>
</div>

The person who has written CSS might have given the hierarchy for .header children. He/She might not have given CSS to parent.

If it doesn't reflect in design after removing it then you can remove it.