Specifically, I'm wondering how this can happen (from Chrome Developer Tools):
My understanding is that it is telling me that the CSS says to make the width 1000px, but the browser decided to make it 985px. How can I track down the root cause of the discrepancy?
I see the same thing in Safari Web Inspector. Specifically, the width value under Rules is 1000px:
while under Computed, the width is 985px:
In case it matters, this particular issue is showing up for a div element.