Question

I got a problem for you to solve, as you know.
I ripped off all my hair trying to figure out why the heck last-child isn’t working.
I tried to remove border-right with last-child but for some reasons, it didn’t work out.
Here’s is the link

Answer 1

Your selector is #countdown .num:last-child.

Your HTML is

<ul ID="countdown">
  <li> <div ID="days" class="num">00</div>  <div CLASS="text">days</div>     </li>
  <li> <div ID="hours" class="num">00</div> <div CLASS="text">hours</div>    </li> 
  <li> <div ID="mins" class="num">00</div>  <div CLASS="text">minutes</div>  </li>
  <li> <div ID="secs" class="num">00</div>  <div CLASS="text">seconds</div>  </li>
  <div class="clear"></div>
</ul>

Think: is .num the last child of its parent? Answer: no.

Your selector should be more like #countdown > li:last-of-type .num, selecting .num inside the last li in #countdown.

Note that in this case last-of-type must be used rather than last-child because you’ve got that <div class="clear"></div>, which is invalid HTML (you can’t have a div directly inside a ul).