I found a solution that worked for me:
I had two similar elements in my html page that I needed to hide working only from the CSS.
<div class="notToBeHidden">
<label class="label aClassToBeHidden" for="aClassToBeHidden">
<div class="forminput aClassToBeHidden">
</div>
<div class="notToBeHidden">
<label class="label anotherClassToBeHidden" for="anotherClassToBeHidden">
<div class="forminput anotherClassToBeHidden">
</div>
I hid the elements by writing in the CSS:
.label.aClassToBeHidden{display: none}
.forminput.aClassToBeHidden{display: none}
.label.anotherClassToBeHidden{display: none}
.forminput.anotherClassToBeHidden{display: none}
Since I hid before id elements by selecting them like:
#elementToBeHidden{display: none}
I didn't know how to use the same concept with elements within classes.
Again, thanks to everyone!