Adding spacer 0 pixel to CSS code

Hi, just wanted to confirm that I would be OK copying this CSS code into the blank CSS window found in the Design section of my site. Scared to commit to it!  

This area will allow you to inject custom CSS rules into your site.

Warning: Adding custom CSS to your site can break your design. Please use caution when using this feature. Our support team will be limited in their ability to help you with design related issues if you have custom CSS.

Note: Custom CSS does not apply to Cover Pages.

/* Add this first bit to get more flexibility in height. */
.sqs-layout.sqs-editing .sqs-block, .sqs-block-spacer-content {
    min-height: 0px !important;
}
.sqs-block-spacer .sqs-block-content {
  height: 0;
}

/* Add this second bit too if you want to be able to go to zero. */
.sqs-block-spacer {
	padding-top: 0 !important;
	padding-bottom: 0 !important;
}

So if I take the bold move and paste it into that empty block, I'll be able to go back to that empty block which will now have that code in, and just cut it? 

If you are pasting code in the custom CSS window in design, and it doesn't do what you want just go back and delete it, that's it. 

OK, thanks!