Before we go out and play, let's talk about specificity, an advanced but important topic.

By deciding which styles to apply, specificity helps us resolve conflicts when multiple declarations try to set the same property.

<html>
 <head><style>#box1 {background: green;}.box {background: red;width: 200px;height: 200px;}div {background: firebrick;border: 2px solid black;}</style></head><body><div class="box" id="box1"></div></body></html>
]]>

See that? It's not the order that tips the balance. Types have a lower specificity than classes, which in turn are less specific than IDs.

That doesn't look right, does it?