Code editor change UI of CABLES

I create simple project with Ops.Html.CSS_v2 class. Put simple code to customize SPAN element and focus color for DIV.

font-size: 20px;

div:focus {
background-color: yellow;

And this code control full UI of CABLES. If I change font size in a code it’s change UI font size too. And if I focus on some div, color is changing too. U can see it on image/