Partially because a designer wrote a lot of these and partially cause I didn't know anything about CSS selector efficiency.  I did a couple google searches though and you are correct that it's not the most efficient to add the 'div' to the selector (https://developer.mozilla.org/en-US/docs/Web/Guide/CSS/Writing_efficient_CSS).  However, the browser will parse the selector from right to left, so it's looking for the id or class first, and then the 'div'.  In essence it only has to check that one element to make sure it's a div and doesn't have to traverse the entire DOM again (http://csswizardry.com/2011/09/writing-efficient-css-selectors/), so the lack of efficiency seems pretty negligible and wouldn't be perceived by the user in a small page like this, unless I'm mistaken.  Good to know for the future though.