Why does Web Inspector show User Agent Stylesheet as 'locked'

Question

I think the easiest way to show this is with a picture:

http://oi61.tinypic.com/r2s4f9.jpg

In Web Inspector, I'm trying to change display:block but it's 'locked'. Further, I can't figure out where this is coming from in my source code

Answer 1

It shows as locked because you are not able to edit it directly using DevTools. You have to override the styles in the user agent stylesheet.