a {
  font-weight: bold;
  text-decoration: none;
  &:hover { text-decoration: underline; }
  body.firefox & { font-weight: normal; }
}

#main {
  color: black;
  a {
    font-weight: bold;
    &:hover { color: red; }
  }
}

@mixin parent {
	&:hover {
		color: blue;
	}
}

.mixin-parent {
	@include parent;
}