I spent way too long trying to remove extra spacing to the left of a select box, when in Chrome Developer Tools, I finally saw that the user agent stylesheet was adding 2px margin-left (looking under the Computed Style). But when I click the margin-left dropdown to see where this style is being defined, it says it's being defined as 0em, as in the following screenshot...can someone explain this to me??

![Chrome user agent stylesheet - how does 2px = 0em?](https://i.stack.imgur.com/vWtgt.png)