How do I lock and unlock the magnify image?
The magnify tool can be locked by pressing the assigned global hotkey (⌃⌥⌘L). This can be determined by looking next to "Lock magnify image", under the "Tools" menu.
To unlock the image, press the same global hotkey again.
Why use shorthand hex values?
The main reason to use shorthand hex values whenever possible is to optimize your cascading style sheets. Using shorthand hex can shrink css files dramatically.