I don't understand why the
font-family: 'Roboto', 'Microsoft JhengHei', sans-serif;
<div class="button" id="yes">
By default the
a tag has underline effect (using text-decoration:underline), So to remove this, you must remove from
a tag not from its child element.
If you are talking like color values can be overridden from parent to child element but why not text-decoration?
This is because the text-decoration property doesn't inherit the style from its parent element but relies upon its own element.
Check w3c reference.