Custom CSS only works in edit mode

Hello!

I'm using css to make a text box reveal on hover over an image. It's pretty straight forward, but it's only working in edit mode, not once I save or in any other viewing browser. 

Here's the code (same/sub block for following sections):

@media only screen and (min-width: 640px){

#block-00eba619a5dcb7f707ea {

opacity: 0;

transition: opacity 1s

}

#block-00eba619a5dcb7f707ea:hover {

opacity: 1;

transition: opacity 1s

}

}

Page: https://labtheater.org/dia-y-noche

The page url doesn't exist. Can you check it again?