permanent solution to borders in 2014

Greetings
Previously I posted regarding table borders in 2014, well at the time it was 2012. I used to be able to insert this into the style sheet border:none !important; and then the borders would go away. But now with the newer updates the borders are back and this is not working anymore.
I am unsure how to make a child css and the code that would make these lines go away but I sure would love it if someone could help